TECHNICAL ENGINEERING 

EVALUATION REPORT (TEER) 

FOR THE 

CHITOSAN-ENHANCED 

SAND FILTRATION TECHNOLOGY 

FOR FLOW-THROUGH OPERATIONS 

Developed by Natural Site Solutions, LLC 

Redmond, Washington

Prepared By 

Gary R. Minton, PhD, PE 

Resource Planning Associates 

Seattle, Washington 

February 28, 2006 
TABLE OF CONTENTS 

TOPIC PAGE 

PART I – BACKGROUND INFORMATION 

Designation sought 1 

Current designations 1 

Consultant’s role 2 

Consultant’s recommendations 3 

Regarding approval of the technology 3 

Regarding further testing 3 

Regarding system specifications 3 

Ecology specifications for the flow-through system 6 

Technology description 9 

General 9 

System components 10 

Recycle 12 

Operation and maintenance manual 12 

Test site descriptions 13 

Lakeside housing development 13 

SeaTac International Airport third runway 14 

WSDOT SR-522 road improvement project 16 

Test program design 17 

PART II – THE CONSULTANT’S EVALUATION 

Systems selected for evaluation 18 

Compliance with Ecology specifications 18 

Compliance with the NSS QAPP 23 

Residual chitosan test 23 

Toxicity evaluation 23 

Laboratory tests of Liqui-Floc 23 

In-situ field tests of treated discharge 25 
TOPIC PAGE 

Meeting the discharge quality specifications 26 

Lakeside housing development 27 

SeaTac International Airport third runway 28 

WSDOT SR-522 road improvement project 29 

Reliability 30 

Factors other than performance 31 

Discussion of factors 31 

Cost 35 

References 37 

APPENDICES 

A. Recommended specifications for CESF-FT facilities 39 

B. Recommended Operating Period Information Form 42 

C. Examples of completed Daily Operation Log forms 43 

D. Operation and Maintenance Manual (separate document) 

E. Chitosan test procedure (separate document) 

F. Certification of chitosan test by AMTEST Laboratories (separate document) 

G. Laboratory tests of toxicity of Liqui-FlocTM (separate document) 

H. In-situ field tests of toxicity of CESF-FT discharge (separate document) 

Appendices D, E, F, G, and H are contained in one separate document. 
Not to be released without written approval by NSS 1

PART I BACKGROUND INFORMATION 

Natural Site Solutions, LLC (NSS) of Redmond, Washington contracted with Resource 

Planning Associates, specifically Dr. Gary Minton (referred to as Consultant), to review 

the ability of the Chitosan-Enhanced Sand Filtration Systems (CESF) to meet conditions 

set forth by the Washington State Department of Ecology (Ecology, 2003b, 2004), and to 

prepare a Technical Engineering Evaluation Report (TEER). The evaluation contained in 

this report is based on performance of systems at three sites: Lakeside Housing 

Development, WSDOT SR 522 Road Improvement Project, and the third runway at the 

Seattle-Tacoma International Airport (SeaTac). These three projects were identified by 

NSS in its application (NSS, 2004b). 

The data were collected following a QAPP Plan (NSS, 2004a), prepared in accordance 

with the protocol developed by the Department of Ecology (Ecology, 2003a). Ecology 

(2003a) sets forth requirements for the evaluation of technologies that chemically treat 

stormwater from construction sites. Ecology (2003a) requires the preparation and 

acceptance by Ecology of a QAPP Plan. A QAPP was prepared by Natural Site Solutions 

(2004a) and accepted by Ecology. The QAPP is available as a separate report and is not 

included in the TEER report. 

DESIGNATION SOUGHT 

Natural Site Solutions of Redmond, Washington seeks General Use Level Designation 

(GULD) to operate the CESF as a flow-through system (termed “CESF-FT” in this 

report), meeting the specifications defined by the Washington State Department of 

Ecology (Ecology, 2004). A flow-through system allows for the continuous discharge of 

treated construction site stormwater directly to surface waters without intermediate 

temporary storage of treated stormwater. The Department of Ecology (2003b, 2004) 

established conditions to be met if GULD were to be given to the CESF-FT system. 

These conditions are described in this TEER. In October 2003, Ecology gave a GULD 

designation for batch treatment with the use of Liqui-Floc,TM a special chitosan acetate 

coagulant. This TEER report documents findings related to seeking designation for the 

continuous flow-through operation. 

CURRENT DESIGNATIONS 

In October 2003, NSS received the following designations (Ecology, 2003) with respect 

to the CESF technology. 

1.General Use Level Designation for the CESF technology with the discharge of Chitosan acetate 

treated water to retention systems capable of infiltrating all storms to the ground with no 

discharge to surface water. The design of the infiltration system must be based on the criteria in 

Volume V of Ecology's 2001 Stormwater Manual for western WA. The design and operational 

criteria for the CESF specified in this document shall also be strictly adhered to. Records 

showing that total retention was achieved must be kept on site. 

2.General Use Level Designation for the CESF technology with a discharge of Chitosan acetate 

treated water from a temporary holding pond to surface water only after the treated stormwater 
Not to be released without written approval by NSS 2

 is demonstrated to contain less than 0.1 ppm residual Chitosan acetate polymer or is non-toxic 

to aquatic organisms (batch treatment). The design and operational criteria specified in this 

document, and in BMP C 250 of Ecology's Western WA Stormwater Manual shall be strictly 

adhered to. The effluent turbidity and pH shall be monitored at a frequency acceptable to 

Ecology. 

3. Conditional Short-Term Use Designation (CUD) for the CESF technology with the chitosan 

acetate treated discharges conveyed directly or indirectly to surface water (flow-through 

system). This CUD expires on December 31, 2005, unless extended by Ecology and takes effect 

when all the applicable “Conditions" and "Design and Operational Criteria" specified in this 

designation document are implemented or satisfied. This CUD will take effect on March 9, 2004 

and will be posted at Ecology’s stormwater web site as soon as possible. 

The designations were updated in August 2004 (Ecology, 2004). 

Ecology (2003b, 2004) established that “Discharges from the CESF system under these 

(the above described) designations: 

• Shall not cause or contribute to a violation of State Water Quality Standards. 

• Shall comply with the discharge requirements of the State of WA Construction 

Stormwater General Permit, AKART, and local government requirements, for 

turbidity and other applicable pollutants. This designation document must be used 

as the basis of SWPPPs for all construction projects where chitosan treatment is 

planned. 

 

• Shall be consistent with the guidance in BMP C250, Construction Stormwater 

Chemical Treatment, of Ecology's 2001 Stormwater Management Manual for 

western WA. 

• Are expected to achieve performance goals of a minimum of 95% reduction of NTU 

turbidity, a maximum discharge of 10 NTU turbidity, and a discharge pH within a 

range of 6.5-8.5. If these values are exceeded at any time the responsible site 

operating personnel shall immediately take appropriate corrective actions.”

CONSULTANT’S ROLE 

The TAPE specifies that the applicant is to hire an independent consultant stating “the 

following work must be performed by an independent professional: 

1. Complete the data validation report. 

2. Prepare a TEER summary, including a test results summary and conclusions 

compared with the supplier’s performance claims. 

3. Provide a recommendation of the appropriate technology use level. 

4. Recommend relevant information to be posted on Ecology’s website. 

5. Provide additional testing recommendations, if needed.” 

Item 4 is not presented in this report. Information to be posted on the website can be 

generated subsequent to a decision by the Department of Ecology should it be favorable. 
Not to be released without written approval by NSS 3

CONSULTANT’S RECOMMENDATIONS 

Regarding approval of the technology 

Recommendation #1: Approve the CESF-FT technology. 

The Consultant recommends that the continuous flow system be approved for GULD. 

Regarding further testing 

The Consultant makes the following recommendations: 

Recommendation #2: Bioassays with marine organisms

As yet, bioassays have not been performed on marine organisms. This should occur prior 

to the use of the CESF-FT where discharge to marine waters is to occur. 

Recommendation #3: In-situ toxicity tests at high turbidity concentrations 

As specified by Ecology, an in-situ evaluation of the toxicity of Liqui-Floc was evaluated 

as a function of dosage and turbidity. The results are reported in this TEER. However, 

the study was conducted only up to a turbidity of 500 NTU. It is recommended that the 

test be extended to several thousand NTU. It is not uncommon for these higher levels of 

turbidity to occur in untreated stormwater, necessitating pretreatment with Liqui-Floc. 

Regarding system specifications 

NSS does not typically design, install, operate or maintain CESF facilities. It is the 

responsibility of the site contractor. Consequently, each construction site permit for a 

CESF-FT facility issued by Ecology should contain specifications related to design, 

operation, and maintenance similar to those developed previously (Ecology, 2003b, 2004). 

To support this effort the Consultant has prepared recommended specifications reflecting 

the experience gained with the test program reported in this TEER. The recommended 

specifications are presented in Appendix A. Presented below are the more notable changes 

to the specifications previously developed by Ecology. 

Recommendation #4: Raise the limit for the residual concentration of chitosan to 0.2 

mg/L. 

Ecology currently specifies that the concentration of residual chitosan not exceed 0.1 

mg/L in the discharge. However, AMTEST Laboratories has determined that the test 

procedure provides a reliable result to 0.2 mg/L only. This residual concentration remains 

substantially below concentrations at which toxicity occurs. It is therefore recommended 

that Ecology raise the limit to 0.2 mg/L. Refer to Page 26. 
Not to be released without written approval by NSS 4

Recommendation #5: Allow variances to the maximum allowable dosage rate of chitosan 

acetate. 

Ecology specifies a maximum dosage of 1 mg/L. The system can be operated within this 

limitation if the turbidity of the untreated stormwater entering the holding basin is less 

than 600 NTU. Experience from the test program indicates that despite full 

implementation of erosion control practices, the turbidity of the stormwater entering the 

holding basin can exceed 600 NTU. This necessitates enhanced pretreatment with the use 

of an initial dosage of chitosan as the stormwater enters the holding basin. The need for 

this action will vary with the site. It was found necessary at one of the three test sites. 

Ecology gave variances at these two sites. Although dosages as high as 3 mg/L were 

used, the effluent residual chitosan was always below the detection limit of 0.2 mg/L. 

The variance should be allowed but only for pretreatment where the applicant can 

demonstrate pretreatment with chitosan acetate is necessary because of the type of project 

or soil conditions. Dosage immediately before the filters should be limited to 1 mg/L. The 

most common type of project where a variance is likely needed is the linear roadway 

project where equipment movement inhibits full use of source control BMPs. 

Recommendation #6: Modify the language of the discharge requirement. 

The language currently reads: Are expected to achieve performance goals of a minimum 

of 95% reduction of NTU turbidity, a maximum discharge of 10 NTU turbidity” ... 

Consider the following: If the influent concentration is only 20 NTU, the discharge 

requirement becomes 1 NTU. This is not technologically feasible. If the influent is over 

200 NTU, the effluent turbidity of 10 NTU must be met and therefore the efficiency must 

exceed 95%). The words: “minimum of 95%” should be deleted. 

Recommendation #7: Modify the language of the discharge monitoring requirements.

Ecology has specified “Water quality influent and effluent shall be continuously 

monitored for pH and turbidity and the effluent for chitosan concentration and/or aquatic 

toxicity as follows.” The word “and” in the term “and/or” should be deleted. As written, 

it states that toxicity must be continuously monitored even if the chitosan concentration is 

measured. The following verbiage is recommended: “Water quality influent and effluent 

shall be continuously monitored for pH and turbidity. The effluent should be periodically 

monitored as specified in the SWPPP for either chitosan concentration or aquatic 

toxicity”

Recommendation #8: Limit approval at this time to the Liqui-FlocTM polymer for 

continuous operation. 

There are several forms of chitosan acetate. Proprietary considerations limit the ability to 

specify the form of chitosan acetate developed by each manufacturer. The Consultant 

therefore recommends that Ecology not give generic approval for the use of all potential 

forms of chitosan acetate. Rather, the treatment effectiveness and toxicity effects of each 

product must be considered. Each form of chitosan acetate offered for use should undergo 

full field and laboratory testing, including toxicity tests. These tests should be conducted 
Not to be released without written approval by NSS 5

through the full ranges of turbidities and pH values expected to occur. In addition, the 

efficacy of the test procedure presented in this report for residual chitosan must be 

evaluated for each new type of chitosan acetate proposed for use. 

Recommendation #9: Concerning calibration of the chitosan dosage pump 

The current specification is that the pump be calibrated at the onset of each operating 

period and every four hours. The Consultant’s review of the operating records indicates 

that the metering pump is very stable. It is therefore recommended that the pump be 

recalibrated only when the flow and/or influent turbidity changes significantly. 

Recommendation #10: Record the rate of discharge 

With the CESF-FT system the pH and turbidity of the treated stormwater is continuously 

and automatically monitored. Should the quality of the treated stormwater not lie within 

the discharge specifications the system automatically recycles the stormwater to the 

holding basin for further treatment by actuating valves. 

At the three test sites, the discharge flow rate immediately downstream of the recycle 

value was monitored. However, only the total flow during the operating period was 

recorded, not the continuous record. Whether a particular recycle event occurred can only 

be inferred from the record of pH and turbidity values, rather than by a direct record of 

discharge flows. Recording the discharge flow would indicate periods when the flow is 

zero, reflecting the failure to meet the discharge requirement. Such a record gives the 

local or state inspector assurance that each time the pH or turbidity specification is not 

met, the recycle mode actually occurred. 

Recommendation #11: Require the use of an Operating Period Information Form 

A stormwater treatment facility involving continuous discharge should maintain 

operational records. This allows the regulator to confirm performance. The Consultant 

makes the following suggestions regarding record keeping. A standard form should be 

completed for each operating period, called an Operating Period Information Form. The 

recommended form is presented in Appendix B. Operators at the three tests sites were 

completing a similar form. Appendix B is similar to the form that was used, but modified 

based on recommendations of the Consultant. The Consultant’s recommendations stem 

from a review of the records of the three sites, discussed further in this report. 

It is further recommended that the supervisor of the operator examine weekly the 

accumulated completed forms. The supervisor should sign each form to indicate that it 

has been reviewed, and should also document any actions he or she takes in response to 

any abnormal conditions observed by the operator. 

Recommendation #12: The specifications outlined in Appendix A replace BMP C250 in 

the Department of Ecology stormwater manuals for Washington. 

The objective is to avoid confusion and the potential for misinterpretation in attempting to 

resolve any differences with BMP C250 and the proposed specifications. 
Not to be released without written approval by NSS 6

ECOLOGY SPECIFICATIONS FOR THE FLOW-THROUGH SYSTEM 

Ecology (2003b, 2004) established conditions for the approval of a flow-through system. 

NSS used these as specifications to guide its test program, embodied in the QAPP 

document (NSS, 2004). 

1. The approved Quality Assurance Project Plan (QAPP), dated January 12, 2004 must be 

followed and includes: 

• A field procedure for detecting a residual of chitosan in stormwater discharges greater 

than 0.1 ppm which has been accepted by Ecology. It can be downloaded by clicking 

“Colorimetric Determination of Residual Chitosan in Treated Stormwater.” 

• Additional bioassay testing that is acceptable to Ecology's Randy Marshall including one 

in-situ bioassay test. Laboratory-based EC25 testing will also be necessary for the 

following receiving water conditions: 

o juvenile salmonid or other fish rearing or habitat, 

o salmonid or other fish spawning, 

o lakes, 

o marine waters, 

o sensitive marine habitat. 

Note: The bioassay test protocols must be pre-approved by Ecology's Randy 

Marshall and typically will include EC25 and 7-day survival determinations, including 

testing with embryos. The tests could be conducted once either before a project SWPPP is 

prepared or ASAP to finish the bioassay testing for the projected receiving waters. If toxicity 

is revealed NSS will notify Ecology immediately that it set Chitosan use restrictions to the 

degree applicable for that particular species and receiving water. 

• A selection process for pretreatments for influent turbidities above 600 NTU, • A clear 

explanation (including appropriate graphics) of the relationship between pH and Chitosan 

effectiveness for turbidity removal. It is desirable to illustrate the decrease in effectiveness 

when the pH approaches the optimum of 6.5-8.5. 

• The sand filter operating indicator(s) for switching to the backwash cycle (pressure drop, 

effluent turbidity, etc.) The chitosan dose rate shall not exceed 1 mg/L (as chitosan acetate 

by weight) or 100 mg/L as 1% Liqui-Floc and not exceed 50 mg/L as 2% Liqui-Floc. 

2. Water quality influent and effluent shall be continuously monitored for pH and turbidity and 

the effluent for chitosan concentration and/or aquatic toxicity as follows: (NOTE: All aquatic 

toxicity test procedures must be approved by Ecology’s Randy Marshall prior to 

implementation). For the continuous flow-through discharge to surface water under the CUD 

the following monitoring and operating procedures shall be strictly followed at all sites until a 

General Use Level Designation is issued by Ecology: 

a. The metering pump must be calibrated at startup of the CESF and every four hours 

during the operation of the Chitosan metering pump to ensure that the dosage is at or 

below 1.0 ppm at all times. All calibration results must be recorded simultaneously 

with the flow rates and the records kept on site. 
Not to be released without written approval by NSS 7

b. The discharge from the sand filters must be maintained below 0.1 ppm residual 

chitosan acetate polymer at all times. At least two discrete grab samples of a 

homogeneous sand filter discharge must be collected during each operating period 

(CESF continuous operation up to 24 hours) and analyzed for residual Chitosan 

polymer. The samples must be collected one and two hours after the onset of each 

operating period. 

c .In the event that the chitosan residual in the discharge is greater than 0.1 ppm, or the 

discharge exhibits aquatic toxicity based on approved bioassay testing, or when the 

CESF system is upset or fails a contingency plan to immediately correct the problem 

must be included in every SWPPP under this CUD. The contingency plan can include 

any of the following emergency operational measures, or equivalent measures for the 

handling of the "off-spec" stormwater: 

• temporary storage sized to handle all reasonable failure scenarios, 

• discharge to a sanitary sewer if available and pre-approved by the sewer authority, 

• discharge to an infiltration system with no discharge to surface water, or, 

• truck hauling for proper disposal until the problem is corrected. 

d. At one or more construction sites and at any site that is not monitored for residual 

chitosan in the sand filter discharge operate an insitu bioassay test following a 

protocol that has been approved by Ecology (Randy Marshall). 

e. At all construction sites, at the end of each 8-hour shift, a delegated responsible person 

must record his/her assessment of the operational efficiency of the CESF process and 

all upsets, the insitu bioassay results (where applicable), the sand filter discharge 

chitosan concentrations (where applicable) and any other relevant observations that 

relate to CESF proper operation and must also certify the acceptability of the CESF 

discharge to surface water. 

f. Stormwater discharges from the CESF system shall not cause or contribute to receiving 

surface water quality violations. If the discharge from the CESF will be to a fish 

spawning area in the stream an approval for that discharge must be obtained from the 

responsible Ecology Regional Office. NSS guarantees that CESF, when used as 

directed, will not produce treated water which exhibits aquatic toxicity caused by 

Chitosan added as a treatment agent. 

3. Source Control procedures will be implemented to the maximum extent feasible to minimize the 

need for Chitosan treatment and for controlling the influent NTU to less than 600. 

4. During periods of operation of the CESF system a qualified operator acceptable to NSS must 

be present on-site. 

Additional requirements identified as “Design and Operational” include: 

1. The CUD and GULD apply only to Vanson/HaloSource Storm Klear Liqui-Floc (1% and 2% 

chitosan acetate) Chemical Abstract Service number 9012-76-4 

. 

2. Because of the high solids loading in water associated with construction siterunoff CESF 

systems must be designed and operated at a flow rate not to exceed 15 gpm per square foot of 

sand bed filtration area and should employ a minimum of three (3) sand filter pods to ensure 

adequate backwashing capacity. The backwash slurry from the sand filters must be 

discharged to a detention cell that is separate from the temporary storage cell for the 
Not to be released without written approval by NSS 8

incoming turbid stormwater. The overflow from the backwash slurry detention cell can 

overflow into the detention basin for the turbid stormwater. 

3. The maximum suspended sediment (expressed as turbidity) of the influent water should not 

exceed 600 NTU. 

4. The CESF system treated water output shall be equipped with an automatic integrated 

turbidity and pH sensors capable of shutting the system down if output turbidity or pH exceed 

preset values. An audible alarm and warning light will be installed on the treatment system to 

alert the operator in the event of a system failure. NSS is encouraged to include a 

computerized controller (like the Talus system) to automatically adjust chitosan dosage based 

on turbidity, flow, and pH. 

5. The only filtration media approved is a pre-washed #30 crushed silica sand with a mean 

effective sand size of 0.34 mm and a filtration quality mesh of 230-400. Minimum sand bed 

depth shall be 18-inches underlain with a minimum of 6-inches of 1-inch crushed rock. An 

intermediate mesh-siz garnet may be added to enhance performance. 

6. Chitosan injection shall be performed with an LMI-brand C77, high viscosity pump head, 

electric metering pump, or equivalent. The CESF system shall include a flow-regulating valve 

on the input to and output of the sand filter. These regulating valves will reduce the maximum 

output of the pump as required and facilitate proper backwash. 

7. The CESF system (including metering pump, chitosan storage and instrumentation) shall be 

completely enclosed in a secure structure with locking door. The Chitosan liquid concentrate 

tank, metering pump and tubing shall be completely contained for secondary containment. The 

metering pump discharge tubing shall have an anti-siphon valve. 

8. Jar tests will be conducted, as needed, to confirm the dosage level of Liqui-Floc. 

9. During the planning (SWPPP preparation, etc.) of a project the adverse potential impact on 

chitosan efficiency of the use of anionic polymers for soil blanketing and stability, will be 

evaluated. 

10. The CESF system shall only be operated by a trained technician certified through an 

approved training program including classroom and field instruction. Training to be provided 

by Natural Site Solutions to include the following Minimum Training Requirements: 

Prerequisites: 

• Minimum 1-year experience with, and sound working knowledge of, high pressure sand 

filter systems. 

• Experience deploying and troubleshooting pressurized water pumping and piping 

systems. 

• Fundamental knowledge of stormwater discharge regulations for applicable 

region/locale. 

• Fundamental knowledge of stormwater quality testing procedures and methods for 

parameters applicable to the region/locale.(note: class and field content is specified 

but not included here) 
Not to be released without written approval by NSS 9

TECHNOLOGY DESCRIPTION 

The QAPP prepared by Natural Site Solutions (NSS, 2004a) contains a detailed 

description of the technology, and the options available in the event that effluent 

requirements are not met. Provided below is a brief summarization. The reader is referred 

to the QAPP for the more detailed description. 

General 

Chitosan-Enhanced Sand Filtration is a stand-alone treatment technology for stormwater 

from construction sites. Chitosan acetate coagulates fine suspended sediments, producing 

larger particles, enhancing their retention by the treatment system. Operating the 

Chitosan-Enhanced Sand Filtration system (CESF-FT) in the flow-through scheme 

avoids the need for a large and costly holding basin for treated water. If operated as a 

batch system, a minimum of three holding basins would be needed: one for untreated 

stormwater and two for treated stormwater. Avoiding the second holding basin increases 

the number of sites where CESF-FT may be feasible. A schematic is shown in Figure 1, 

using the system employed at the SeaTac International Airport, one of the three test sites. 

Stormwater is initially retained in a holding basin, which serves two functions. It 

provides pretreatment by one and possible two modes. The common pretreatment mode 

is simple gravity settling of sediment entering with the untreated stormwater. 

Pump

Stormwater Detention Pond

Chitosan-Enhanced Sand Filter System

Chitosan

Chitosan storage/metered pumping 

& water monitoring trailer

Construction Site Stormwater

Conveyed to Detention Basin

Backwash Water

Treated 

Stormwater

Discharged to 

Snohomish River

Figure 

Seatac Airport CESF System 

Schematic

Turbidity and pH Controller

Influent 

Sample 

Port

Effluent 

Sample Port

Automatic 

Recycle 

Valve

Automatic 

Recycle 

Valve

Influent pH & 

Turbidity 

Monitoring

Effluent pH & 

Turbidity 

Monitoring

Flow Meter 

& Totalizer Flow Meter 

& Totalizer

Pump

Chitosan 

Pretreatment 

Line

Chitosan 

Treatment 

Line

20,000-gallon 

Pretreatment 

Tank

20,000-gallon 

Pretreatment 

Tank

20,000-gallon Backwash 

Settling Tank

FIGURE 1 CESF-FT Schematic 
Not to be released without written approval by NSS 10

System components 

The second pretreatment mode is the addition of chitosan acetate as the stormwater enters 

the basin. This is done only if the incoming stormwater is extremely turbid, in excess of 

600 NTU and if all source control measures have been found incapable of reducing the 

turbidity below that value. The second function is to equalize the flow rate. Moderating 

the incoming flow allows the CESF-FT to operate at an essentially constant flow rate. 

The filters are periodically backwashed automatically to remove filtered sediment from 

each pod to maintain the hydraulic capacity of the sand. This feature allows the treatment 

system to operate on a continuous flow-through basis. As shown in Figure 1, the system 

typically has four filter pods. The system is equipped with automated sensors for turbidity 

and pH. If the discharge requirements are not met for either, the treated stormwater is 

recycled to the holding basin, to receive treatment again. Chitosan acetate is added 

immediately before the filters. 

The CESF-FT consists of these components. 

Stormwater holding basin(s): Alternatively called the detention/pretreatment basin, 

these may be either temporary or an element of the permanent drainage system (i.e. 

detention basin), and may be either ponds or mobile storage tanks. 

Pretreatment: Axiomatic to the treatment system is good site erosion control. The 

objective is to keep the turbidity of the untreated stormwater less than 600 NTU. 

When the turbidity of the stormwater entering the holding basin exceeds this value, 

chitosan acetate is added as the stormwater enters the basin or a pretreatment tank 

that follows the basin. The latter has been the more common practice. The pretreated 

water then enters the basin or tank where the coagulated sediment settles. 

Influent pump: Stormwater is pumped from the holding basin to the filter units. 

Liqui-Floc injection system: Consists of the following: precision, variable output 

metering pump, feed and suction tubing, Liqui-Floc product storage container. 

Discharge piping or structure: Site and flow rate specific. 

Sand filtration units: Various sizes and capacities are shown in Table 1 (NSS, 

2004b). The sand size specification (NSS, 2004b) is presented in Table 2, consistent 

with Ecology (2003b, 2004) requirements. The filters are operated in the range of 5 

to 10 GPM/ft2

 of media. Eighteen (18) inches of sand is used. 

Backwash system: The sand filters are periodically backwashed to retain their 

hydraulic capacity. The frequency of backwashing is controlled by a timing 

mechanism, causing backwashing to occur on a regulator schedule. The control 

system also contains a default value for pressure loss through the filter. If the default 

value is reached before the preset time has passed, backwashing occurs. This 

commonly indicates a need to inspection and possibly maintenance of the filters. 
Not to be released without written approval by NSS 11

TABLE 1 Typical Sand Filtration System Capacities 

Manufacturer’s 

Recommended 

Flow Rate2

Min./Max. 

(gpm)

ChitosanEnhanced 

Recommended 

Max Flow 

Rate3

(gpm) 

Inlet/

Outlet

Size

Backflush

Size

Gravel/Sand

Required 

(Bags)

Minimum 

Pad Size 

Required

Approx. Ship 

Wt. 

Less Media

(lb)

90 / 132 80 3” 1 1⁄2” 6 / 6 4’ x 7.5’ 396 

160 / 237 142 3” 2” 6 / 12 4’ x 9’ 510 

255 / 375 225 4” 2” 12 / 15 5’ x 10.5’ 863 

357 / 525 315 6” 4” 15 / 21 5’ x 12’ 1208 

638 / 938 562 6” 4” 30 / 39 6’ x 15’ 1900 

850 / 1250 750 8” 4” 40 / 52 6’ x 19’ 2580 

TABLE 2 Specification for #30 Grade Crushed Silica Sand Media 

TABLE 2-2 # 30 GRADE SAND SPECIFICATION 

Sieve Size 

(U.S.) 

Cumulative 

Percent Passing 

Individual Percent 

Retained 

16 >99.9 Trace 

20 99.7 0.3 

30 90.6 9.1 

40 28.3 62.3 

50 4.1 24.2 

70 1.4 2.7 

100 0.4 1.0 

140 0.1 0.3 

200 Trace 0.1 

Backwash holding tank: The dirty backwash water does not directly enter the 

holding basin. Rather, it first enters either a small cell located in the holding basin 

(separated from the remainder of the basin by a silt curtain) or a separate tank. This 

keeps most of the filtered sediment from entering the larger basin. 

Influent and effluent turbidity and pH monitoring units: These meters 

continuously sample the influent and effluent, and directly control the recycle valve. 

Data are stored. 

Recycle system: If either the effluent turbidity or pH meter indicates that the quality 

of the effluent has strayed outside the specified discharge requirements, a value 

automatically shifts to recycle the stormwater back to the holding basin. Action is 

then take to redress the cause. 
Not to be released without written approval by NSS 12

Recycle 

Recognizing the importance of recycle, a more detailed discussion is presented. The 

CESF-FS at the Seatac Airport and the WSDOT SR522 sites both have automatic 

recycle, which puts the system into recycle in the event the stormwater does not meet preprogrammed set points for pH and turbidity. The water is returned to the holding basin 

and is retreated. The recycle system has three components to ensure compliance and to 

prevent the release of stormwater outside discharge specifications. 

• Two electronic-actuated, hydraulic pressure-sustaining valves 

• Continuous monitoring consisting of two pH and two turbidity probes 

• Electronic controller to control the recycle valves 

The CESF-FT system is able to recycle water at two points: immediately before and 

immediately after the filters. Chitosan acetate is injected into the pipe carrying 

pressurized turbid water from the holding basin to the filters. The pH and turbidity are 

measured and recorded by a controller. If the influent pH or turbidity is outside set limits, 

the controller sends an electronic signal to the influent recycle valve. The valve opens 

forcing the water into recycle, returning to the holding basin. The audible and light 

alarms activate to alert the operator that the system is recycling. 

The discharge of treated water from the sand filters is measured for pH and turbidity. 

These measurements are sent to the controller and stored. As with the above influent 

recycle, if the pH or turbidity of the effluent is outside discharge limits the controller 

sends an electronic signal to the recycle valve and the valve opens forcing the water into 

recycle. This water is also recycled back to the holding basin. Should recycle occur, the 

audible and light alarms are activated to alert the operator. 

The recycle valves default to the open position (initiating recycle) in the event of a power 

failure or other non-ordinary condition. The valves may also be operated manually. 

OPERATION AND MAINTENANCE MANUAL 

NSS has prepared a standard Operation and Maintenance Manual (NSS, 2003), provided 

as Appendix D (separate document). The major elements of the manual are: 

• Stormwater treatment with chitosan 

• Treatment system planning 

• Treatment system operation 

• Troubleshooting 

The manual includes: a typical treatment system diagram, system specifications, system 

capabilities, Liqui-Floc injection rate table, sample system checklist and operation period 

information form, polymer metering pump specifications, process control equipment, and 

MSDS. The manual supplements and does not replace the manual that should be provided 

by the vendor of the equipment. 
Not to be released without written approval by NSS 13

TEST SITE DESCRIPTIONS 

The QAPP specified that the CESF-FT technology was to be evaluated at three sites. 

Presented in Table 3 are the three sites, the period of operation, and land use. A detailed 

description of each site follows Table 3. 

TABLE 3 Test Sites 

SITE 

PERIOD OF 

CESF-FT OPERATION BRIEF DESCRIPTION 

Lakeside Housing Development November 2003 – February 2004 80 acre housing development 

SeaTac International Airport 

Third Runway 

November 2004 to current 150 acre, earth moving and filling 

project 

WSDOT SR 522 Road 

Improvement Project 

December 2004 to Current 125 acres 

Lakeside Housing Development 

The project was located immediately east of NE 65th and 188th Lane NE. in Redmond. 

Stormwater from the site normally drains east to a natural wetland, then to Evans Creek. 

However, because of the sensitive nature of Evans Creek, all treated stormwater 

generated during the construction period was pumped to the SR 202 stormwater drainage 

system, which discharges directly to Lake Sammamish. The CESF-FT facility at the 

Lakeside Housing Project did not require pretreatment. Figure 2 presents a schematic 

and pictorial view of the filter facility. 

All stormwater runoff from disturbed portions of the site was directed, via open channels 

and storm drains, to the stormwater holding basin, which has a capacity of approximately 

1 million gallons. Treated water from the CESF-FT facility was directed to two treated 

water holding tanks so that the water could be tested prior to discharge. 

Recycle 

Chitosan storage & 

Metering Shack

Sand Filter

Discharge to

Storm Sewer

N

Pumps

Backwash Water

Stormwater Holding Basin

(1 Million Gallons)

Lakeside Housing Development

Treatment System Layout

Figure 2 Lakeside Treatment System Schematic and filter system
Not to be released without written approval by NSS 14

Chitosan (1% solution of chitosan acetate) was injected into a 6-inch pipe about 50-feet 

upstream of the sand filter at 0.3 to 0.8 milligrams per liter (mg/L), varying with the 

turbidity of the water. The dose rate of chitosan was calibrated by timing the uptake of 

chitosan (through the metering pump) from a graduated cylinder and noting the flow rate 

of water from the sand filter. 

SeaTac International Airport Third Runway 

Over 14 million cubic yards of fill dirt are being brought to the west side of Sea-Tac 

International Airport to form the foundation for the new runway, distributed on 150 acres. 

There are seven individual CESF-FT units placed at four separate locations, each with 

holding basins. Their combined capacity is 3,500 GPM. Stormwater can be pumped 

between ponds to maximize the use of the total capacity of the units. Discharge is to 

Miller Creek. 

Stormwater runoff commonly enters the holding basins at a turbidity level above 1,000 

NTU, sometimes as high as 3,000 NTU. The Conditional Use Designation document 

(Ecology, 2004) limits the chitosan acetate dose rate to 1 mg/L. The contractor was able 

to keep the dosage within 1 mg/L, despite the high turbidity, by splitting usage between 

pretreatment and treatment before the filters. At this site, pretreatment occurred in a 

pretreatment tank immediately following the holding basin, not in the holding basin. The 

schematic of one of the facilities is presented in Figure 3. Pictorial views are presented in 

Figures 4 and 5. 

Pretreatment Tank Backwash Settling Tank

Sand Filter System # 4

Recycle 

Generator

Pump

Control System

Pump

Discharge to Miller Creek

N

Pretreatment Tank

Discharge from System #01

Pond G2

Settling Basin

Sea Tac Airport

Pond G2 Treatment 

System # 4 Layout

Figure 3 Sea-Tac International Airport System Schematic (Facility #04) 
Not to be released without written approval by NSS 15

 

 Figure 4 Aerial view of Facility #4 

 Figure 5 Ground view of Facility #4 

Pond G2 Pond G1 

Sand Filter #04 

Discharge to 

Miller Creek 

Backwash 

Pretreatment Settling Tank 

Tanks 

Sand Filter #04 

Chitosan storage, metered 

dosing and monitoring box Power Supply 
Not to be released without written approval by NSS 16

WSDOT SR-522 Road Improvement Project 

The Washington Department of Transportation (WSDOT) is widening SR-522 between 

the Echo Lake Road and a bridge across the Snohomish River. The project site is about 

125 acres: Discharge is to the Snohomish River. A general view of the site and a filter 

unit is presented in Figured 6 and 7, respectively. 

 Figure 6 WSDOT SR-522 Project Figure 7 Filter Unit 

Two 500 GPM units were deployed, one each at the Echo Lake interchange and at Elliott 

Road just south of the bridge over the Snohomish River. The Elliot Road system remains 

active at the writing of this report, while Echo Lake was decommissioned in early 2005.

The basic overall design of the Elliot Road system, shown in Figure 8, includes: 

• Liquid carbon dioxide injection at the pretreatment station to reduce pH 

• Liquid chitosan acetate injection for pretreatment at the pretreatment station 

• Holding basin for gravity solids settling 

• Chitosan-enhanced sand filtration 

SR 522

Pretreatment Tank Backwash Settling Tank

Sand Filter

Recycle 

Generator

Pump

Control System

Pump

Detention/Holding Basin

Discharge Manhole to 

Snohomish River

CO2 Injection for pH Control

Chitosan Injection for 

Turbidity Pretreatment

N

Turbidity Curtain 

A

B

C

Residual Chitosan

Sampling Locations1

Floating Pump

Suction

1- High turbidity stormwater was pretreated 

with chitosan before entering the holding 

basin reduce the turbidity load on the sand 

filter. Sample points A, B and C were tested 

for residual chitosan to see if any residual 

chitosan was present in the water. No 

residual chitosan was ever detected.

Figure 8 WSDOT SR522 Elliott Road System Schematic 

Treatment 

System 

Construction/

Drainage Area

SR 522 Widening Project 
Not to be released without written approval by NSS 17

Turbidity levels of incoming stormwater varied significantly, less than 60 NTU to greater 

than 1,400 NTU. High turbidities were due to the frequent blasting of shale on the project 

site. Therefore, chitosan acetate was added to the high-turbidity stormwater immediately 

prior to the holding basin. It was effective, typically reducing the turbidity in the basin to 

less than 60 NTU. Ecology (2003b, 2004) limits the dose rate to 1 mg/L. A variance was 

requested for this site, allowing an aggregate dosage of 3 mg/L, but with 1 mg/L 

remaining as the immediate dosage before the filters. In practice, about 2.5 mg/L was 

used in pretreatment when required, added as the runoff entered the basin, and 0.5 mg/L 

was used immediately prior to the sand filters. 

Disturbance of the sedimentary shale rock created a high pH (as high as 9.6) in dewatered 

groundwater and stormwater. Liquid carbon dioxide was added at the pretreatment station 

to control pH as it entered the basin. Another adverse condition was extensive algal 

blooms occurring in the basin. The atypical growth of algae increased the pH of the 

stored stormwater, necessitating the placement of carbon dioxide as dry ice in the basin. 

The algae growth was the result of a combination of low turbidity (with pretreatment), 

sunlight penetration, and elevated phosphorus concentrations. The latter was believed due 

blasting explosives. The treatment system removed the algae from the water without 

damage to the filters. 

TEST PROGRAM DESIGN 

The test program is described in Section 3 of the QAPP (NSS, 2004a). Table 4 lists the 

key elements of the sampling design. 

TABLE 4 Major elements of the sampling designa

ELEMENT 

Maintain the residual concentration of chitosan below 0.1 mg/L. 

The determination of the residual concentration to occur three times during each operating period. 

A trout bioassay test is to be conducted at one of the test sites. 

A minimum of 20 operating periods are to occur. 

pH and turbidity to be measured at least every 15 minutes. 

Test sites are to be characterized with respect to perviousness, soil type and vegetation, drainage 

area, drainage system, catchment flow rates, system specifications, closest receiving water body, 

pretreatment requirements, site adequacy for operation and testing, and any adverse site conditions. 

That there be sufficient stored water for each operating period to last at least four hours. 

Flow meter with a flow rate totalizer. 

The chitosan metering pump is to be calibrated during each operating period and recorded on the 

Daily System Operation Log. 

Other pollutants to be monitored aside from turbidity and pH are TDS, TP, TN, total coliform, 

metals, pesticides and oil/grease. 

Turbidity to be sampled by automatic flow-through monitors. 

Handheld turbidity and pH meters to be calibrated daily, system flow meter to be calibrated as per 

manufacturer’s specifications 

A Daily System Operation Log is to be maintained, completed for each operating period. 

NSS (2004a) 
Not to be released without written approval by NSS 18

PART II – THE CONSULTANT’S EVALUATION 

SYSTEMS SELECTED FOR EVALUATION 

The three test sites in combination had ten treatment units. The Lakeside site was 

dismissed because it was operated prior to the final specifications by Ecology (Ecology, 

2004). Consequently, its configuration and operation did not fully meet the specifications. 

Three units were selected, Unit 4 at the SeaTac Airport site which consists of two units, 

and the Elliot Road unit at the SR522 site. The former was selected because these two 

units use the 48-4 sand filter (48” diameter, 4 pods), which is the most popular brand and 

size of sand filter in use with chitosan-enhanced sand filtration. It was also selected 

because pretreatment by chitosan acetate addition is performed in mobile settling tanks 

(in series), rather than the holding basin (see Figure 5), which has become the primary 

configuration for the CESF-FT system. SeaTac Unit 4 represents the best technology and 

configuration therefore will continue to be recommended to contractors by NSS 

(MacPherson, pers.com.). The Elliott Road unit was chosen from the two units at the 

SR522 site because it processed a larger quantity of stormwater and continues in 

operation. 

COMPLIANCE WITH ECOLOGY SPECIFICATIONS 

Ecology (2003b, 2004) established specifications for approval of CESF-FT operation. 

These specifications are listed in detail in this report beginning on Page 6. Table 5 lists 

each stipulation with the Consultant’s conclusions. For many of the specifications, 

reference is made to discussions elsewhere in this report. The Consultant evaluated the 

extent to which these specifications were met by NSS at SeaTac and SR522. Evaluation 

was accomplished through interviews, site visits, and review of operational records 

available at the office of NSS. 

Ecology specifications required monitoring activities other than just effluent turbidity and 

pH. Other operational specifications of particular interest listed below are discussed by 

the Consultant, beginning on Page 21. 

#5 - If exceeded at any time the responsible site operating personnel shall immediately take 

appropriate corrective actions. 

#11 - Chitosan acetate dose rate shall not exceed 1 mg/L 

#13 - Chitosan in effluent below 0.1 ppm residual 

#15 – Chitosan metering pump calibrated at startup of the CESF-FL and every four hours 

#16 - At the end of each 8-hour shift, record assessment of operational efficiency, upsets, etc 

The number of each requirement discussed below relates to Table 5. The Consultant 

examined at random operational records from two sites: SR522 and SeaTac, specifically 

Unit #4. The entire record of each was not examined: rather, randomly selected months. 

Each operational record prepared during the selected months was examined. The 

following are the Consultant’s findings.
Not to be released without written approval by NSS 

TABLE 5 ABBREVIATED LIST OF SPECIFICATIONS OF ECOLOGY FOR THE CESF-FT (See Page 5) # STIPULATION CONSULTANT’S CONCLUSIONS 1 Comply with Construction Permit, AKART, etc. This is an expectation placed on the construction permit with each applicatio

directly related to the TEER. 

2 Be consistent with BMP C250 (Ecology, 2001) This specification was met. 3 95% reduction of NTU turbidity, a maximum of 10 

NTU, discharge pH of 6.5 to 8.5. 

This specification was met. See presentation of data beginning on Page 26. 

4 Stormwater discharges from the CESF system shall not 

cause or contribute to receiving surface water quality 

violations. 

This specification is met by meeting the discharge requirements specified fo

5 If discharge exceeded at any time, the responsible site 

operating personnel shall immediately take appropriate corrective actions.” 

The standard procedure is to recycle the treated water back to the holding ba

control is automatic, based on continuous monitoring of effluent pH and turb

6 Follow the QAPP Consultant concludes the QAPP was followed with exceptions. See discu

#15 and #16, beginning on Page 21. 

7 Additional bioassay testing acceptable to Ecology's 

Randy Marshall for juvenile salmonid or other fish rearing or habitat, salmonid or other fish spawning, lakes, marine waters, or sensitive marine habitat. 

Results summarized beginning on Page 23. Studies enclosed in Appendices agreed to by Randy Marshall of Ecology. Tests as yet have not been performNSS has as yet not been responsible for a site that discharges to marine wate(McPherson, pers. comm.) 

8 Conduct in-situ bioassay test following a protocol 

approved by Ecology. 

Specification was met. See Page 25 and Appendix H. 

9 Explanation of relationship of pH and turbidity 

removal. 

There is no relationship because the two are independent. The CESF dosin

is affected by site conditions such as exposure of fresh concrete to stormwat

10 Use only Vanson/HaloSource Storm Klear Liqui-Floc. This specification is included in each site SWPPP. 11 Chitosan acetate dose rate shall not exceed 1 mg/L. The Consultant examined selected operational records and confirmed tha

Page 21. A variance was received at one of the three sites for reasons expla

12 Influent and effluent continuously monitored for pH 

and turbidity. 

This specification was confirmed by the Consultant during a site visit to 

Airport Unit 4 on August 12, 2005, and through a review of operational recnot occur at Lakeside because the facility operated before this stipulation wa

Effluent testing at this site was manual. 

13 Chitosan in effluent below 0.1 ppm residual. The Consultant examined selected operating data at random: see Page 22

specification was always met. 

14 Develop field procedure to detect residual chitosan 

greater than 0.1 ppm. 

A method has been developed. See Appendices E and F. AMTEST evareliable detection limit. It was determined to be 0.2 mg/L. See Page 3 regathe allowable residual concentration. 

15 Chitosan metering pump calibrated at startup of the 

CESF-FL and every four hours of operation. 

The Consultant examined selected operating data at random: see Page 22specification was not always met. 
Not to be released without written approval by NSS 

TABLE 5 ABBREVIATED LIST OF SPECIFICATIONS OF ECOLOGY FOR THE CESF-FT (Continued) # STIPULATION CONSULTANT’S CONCLUSIONS 16 At the end of each 8-hour shift, record assessment of operational 

efficiency, upsets, etc 

See Daily Log form examples in Appendix C. Consultant hathis form to make the specification more explicit to operator

17 Source BMPs to control influent NTU to less than 600. All construction sites are required to implement commonl

BMPs, as specified in site SWPPPs. The experience o

stipulation of 600 NTU cannot be guaranteed. The Consulon a report prepared for the City of Redmond (Minton, 1999

18 Pretreatment (procedure) for influent turbidities above 600 NTU, Water entering the holding basin is periodically monitore

turbidity is above 600 NTU, chitosan is added directly to the holding basin, preferably several feet “upstream”. 

19 Qualified operator present on-site during operations. This specification is specified in each site SWPPP. 20 Flow rate through the filters not to exceed 15 gpm/ft2. Specification met. 21 Minimum of three filter pods. Specification met. 22 Operating indicator(s) for switching to the backwash cycle. This specification was confirmed by the Consultant durin

SR522 and SeaTac Airport Unit 4 on August 12, 2005 and J

23 The backwash discharged to a holding cell within or separate from the 

holding basin. 

Specification met.

24 Maximum influent turbidity of 600 NTU. See Specification #18 in this table. 25 Audible alarm and warning light when discharge does not meet 

requirements for turbidity or pH 

See description of the technology on Page 9. Consultant conduring site visits. 

265 Filtration media is pre-washed #30 crushed silica sand with a mean 

effective sand size of 0.34 mm and a filtration quality mesh of 230-400. Minimum sand bed depth shall be 18-inches underlain with a minimum of 6-inches of 1-inch crushed rock. 

See description of the technology on Page 10. The Consultagradation test to confirm this specification. 

27 Use LMI-brand C77metering pump, or equivalent. Consultant confirmed the specification during site visits. 28 Include flow-regulating valve on the input to and output of the sand 

filter. 

Consultant confirmed the specification during site visits. 

29 Instrumentation, pumps, chemicals enclosed in a secure structure This specification was confirmed by the Consultant during s

SeaTac Airport (Unit 4) on August 12, 2005. 

309 Jar tests conducted, as needed, to confirm dosage level. Specified by site owner in each SWPPP. 31 During the planning (SWPPP preparation, etc) of a project the adverse 

potential impact on chitosan efficiency of the use of anionic polymers 

for soil blanketing and stability will be evaluated. 

Specified by site owner in each SWPPP. 

32 CESF system shall only be operated by a trained technician certified 

through an approved training program 

This specification was met at the three test sites. The responspecification at other sites rests with the site owner. 
Not to be released without written approval by NSS 21

• #5 - If exceeded at any time the responsible site operating personnel shall 

immediately take appropriate corrective actions.” 

NSS was asked by the Consultant to identify the corrections made by operator in the 

event that the quality of the discharge is outside the allowable quality. The following was 

provided (MacPherson, pers. comm..). 

If a pH or turbidity excursion causes the system cause to go into recycle, the 

operator measures the parameters to determine which is out of compliance. If the 

pH is too low, the system is kept in recycle while food-grade sodium bicarbonate is 

added. If the holding pond is large, this may require shutting down the system, and 

mixing water in the pond with pumps until the desired pH is achieved. The system is 

restarted in recycle mode. Once the pH is within acceptable limits the system is put 

back on line. If the pH is too high, dry ice is hand broadcast into the holding pond 

until the pH is acceptable. If high pH continues (e.g. extensive concrete pouring), 

an automated liquid carbon dioxide injection system may be installed. This system 

reads the incoming and outgoing pH, and automatically adjusts the rate of carbon 

dioxide injection. Such a system was installed for a period of time on the WSDOT 

SR522 project due to the high pH caused by the disturbance of alkaline sedimentary 

shale material by construction. 

If the turbidity exceeds the preset limits, one of three adjustments are made: 

increasing the chitosan dose in a pretreatment settling tank, reducing the flow rate of 

the system to allow more settling time, or more extensive treatment. If, for example, 

the holding pond suddenly experiences a significant increase in turbidity due to site 

work or heavy precipitation, the common adjustment is to continue in the recycle 

mode while additional chitosan is added to the stormwater as it enters the basin. If 

this approach is not adequate due to extreme turbidity the system is shut down, 

pumps recirculate the entire holding pond contents while adding chitosan to reduce 

the turbidity to levels consistent with filtration (<500 NTU). If this approach is 

necessary, Department of Ecology and the project contractor are contacted. A plan 

is developed consistent with Ecology’s regulations and project needs. Typically a 

quantity of additional chitosan is estimated based on jar testing; that quantity is 

added while recirculating (mixing) the holding pond with pumps. Once the turbidity 

has been reduced to acceptable levels the system is restarted in the recycle mode 

until it has been determined that the effluent turbidity limits can be met. Once this 

occurs the system is put back on line. Normally, the holding pond is tested for 

residual chitosan to ensure there is no excess chitosan present. The actions are 

documented in a report, summarizing the cause of the problem and the methods used 

to bring the system back into compliance.

• #11 - Chitosan acetate dose rate shall not exceed 1 mg/L 

A variance to 3 mg/L was given at the SR-522 site, allowing up to 2 mg/L for 

pretreatment and 1 mg/L immediately prior to the filters. The operational records for the 

SR-522 site were examined for the months of January 2005 and October 2005. Dosage 
Not to be released without written approval by NSS 22

immediately before the filter was commonly 1 mg/L or less. The Consultant’s review of 

the records indicates that the variance concentration was not exceeded. As stated 

previously, the additional dosage above 1 mg/L to pretreat the stormwater as it enters the 

holding basin. 

At the SR-522 chitosan residuals were measured in the holding basin, prior to treatment 

by the filter (MacPherson, 2006) to ascertain the possible effect of higher chitosan 

dosages on the residual concentration. Samples were taken at three locations in the 

holding basin on 38 days from late April through May 2005. The Consultant has 

reviewed the data, finding no excursions above 0.2 mg/L of chitosan in either the holding 

basin or in the discharge from the system during this test period. 

• #13 - Chitosan in effluent below 0.1 ppm residual 

The same records identified above were examined for this stipulation. In no operational 

period was a residual above 0.1 ppm observed. However, the test was not always 

performed each operational period as required. At SeaTac in October and December 

2004, and March 2005, the test was not performed in 25% of the operational periods. 

However, this omission decreased to essentially 0% in May 2005, and the test was 

commonly performed twice per operational period. In contrast, at SR522, full compliance 

was achieved in the two months examined, January and October 2005. Although the 

residual dosage was maintained at 0.1 mg/L or less, it is recommended that the stipulation 

be changed to 0.2 mg/L. See the discussion of the test on Page 22. 

• #15 – Chitosan metering pump calibrated at startup of the CESF-FL and every 

four hours 

The same records identified above were examined for this stipulation. With respect to 

SeaTac Unit 4, in the early startup month of October 2004 the pump was not typically 

tested at startup, but two to three hours into the operation. The frequency of early testing 

improved in March of 2005, but still did not consistently meet the stipulation. By May 

2005, the pump test always occurred, always within one hour of startup and 90% of the 

time within 15 minutes. In contrast, at SR522 full compliance was achieved in the two 

months examined, January and October 2005. At both sites the pumps were not 

commonly tested if the operational period lasted beyond four hours. 

• #16 - At the end of each 8-hour shift, record assessment of operational efficiency, 

upsets, etc 

The same records identified above were examined for this stipulation. The operator 

infrequently provided commentary. It is the Consultant’s view that the language of the 

form does not make this requirement clear to the operator. The Consultant has made 

recommendations in this report. The Consultant’s recommended form presented in 

Appendix B makes the requirement very explicit. 
Not to be released without written approval by NSS 23

COMPLIANCE WITH THE NSS QAPP 

Section 3 of the QAPP (NSS, 2000a) was examined on this question. All aspects of the 

program design were met with some exceptions. As the specifications of the QAPP are 

essentially the same as the compliance specifications as specified by Ecology (2003b, 

2004), summarized in Table 5, the discussion of compliance with both documents is 

combined in the previous section. The Consultant discussed the exceptions with the 

Applicant, and considered the rationale for each. 

The subject of dosage limits (1 mg/L) has been discussed. All aspects of the QAPP listed 

in Table 4 were met with to two exceptions. Turbidity and pH were not monitored 

continuously at the Lakeside site. But this was because the site was established before 

Ecology established its operational requirements (Table 5) or the completion of the 

QAPP. A second exception was sampling for analytes other than pH or turbidity. NSS 

decided not to sample for phosphorus or metals given the inherent awareness, based on 

studies of stormwater, that little of either metals or phosphorus are in the dissolved state, 

given the high influent turbidity concentrations. Hence, high removals of turbidity and 

TSS will logically in turn substantially reduce phosphorus and metals concentrations. 

The Consultant concurs with this view. The interest with fecal coliform is with 

construction sites where mulches are applied for landscaping. However, this did not occur 

at any of the test sites. Regardless, the Consultant’s review of the professional literature 

indicates that coagulation-filtration systems provide high removals of coliform. 

RESIDUAL CHITOSAN TEST 

As required by Ecology specifications, NSS worked with a certified laboratory, 

AMTEST, to confirm the capabilities of a test procedure for chitosan acetate, developed 

by John MacPherson of NSS. The test procedure is presented in Appendix E. A report by 

AMTEST of the test procedure and certification results is presented in Appendix F 

(AMTEST, 2005).. 

TOXICITY EVALUATION 

Laboratory tests of Liqui-Floc 

A study was conducted by Nautilus Environmental (2004) regarding the toxicity of LiquiFloc. The full report is enclosed as Appendix G. The Consultant has excerpted the full 

text of two sections of the report: the Executive Summary and the Discussion. Each is 

presented below. 
Not to be released without written approval by NSS 24

Executive Summary: “A toxicity testing program was conducted using Storm 

KlearTMLiqui-FlocTM (chitosan acetate), as manufactured and distributed by Vanson 

HaloSource, Inc., Redmond, Washington, in order to meet the requirements specified in a 

Washington Department of Ecology document titled “Risk Evaluation of Proposed 

Treatment Chemicals for Stormwater Runoff”, dated December 8, 2003 (WDOE, 2003). The 

results of this study are provided in this report. 

The program involved conducting a suite of toxicity tests using the product to determine 

which was the most sensitive species, and to determine the “toxic threshold”, defined as the 

lowest 25% point estimate from the various tests. Rainbow trout were demonstrated to be 

the most sensitive species, with a 7-day LC25 of 1.21 mg/L Liqui-Floc. 

Toxicity tests were subsequently conducted to evaluate the toxicity of the product under the 

conditions of varying turbidity. This investigation was conducted because Liqui-Floc is 

removed from solution as a result of its action on suspended particulate and, therefore, the 

application rate differs from the discharge concentration in the presence of suspended 

particulate. Toxicity decreased substantially and linearly with increasing turbidity from a 

96-hr LC50 value for rainbow trout of 1.68 mg/L at 0 NTU to 4.52 mg/L at 500 NTU 

turbidity. After correcting these data using the ratio between the 96-hr LC50 for rainbow 

trout and the toxic threshold in non-turbid water, this resulted in a toxic threshold for LiquiFloc ranging from 1.21 mg/L in non-turbid water to 3.25 mg/L in water with a turbidity of 

500 NTU. 

It should be noted that the actual treatment technology proposed by Natural Site Solutions 

incorporates a clean-up step involving sand filtration after application of Liqui-Floc to 

turbid water, which further reduces residual dissolved chitosan, thus providing an additional 

safety margin beyond that described in this report. 

Discussion: “The data presented in this study show that rainbow trout were 

substantially more sensitive to Liqui-Floc than any of the other organisms tested. 

There was only a minimal difference between the results of acute and chronic 

toxicity tests using rainbow trout, and survival was a more sensitive endpoint than 

growth in the 7-day survival and growth test with this species. The toxic threshold, 

as defined in WDOE (2003) as the lowest 25% point estimate, was 1.21 mg/L for a 7-

day LC25 to rainbow trout. 

Toxicity decreased with increasing turbidity in a linear manner over the range of turbidities 

tested from an LC50 of 1.68 mg/L at a turbidity of 0 NTU to an LC50 of 4.52 at a turbidity of 

500 NTU. This linear relationship was strong with a R2

 value of 0.997. The reduction in 

toxicity associated with turbidity is not surprising, since the product is designed to sorb to 

particulate materials, therefore reducing its bioavailability. 

It is highly likely that an additional loading of suspended sediment associated with 

turbidities higher than 500 NTU would provide a further reduction in the LC50 for this 

product, because the rate of removal of Liqui-Floc from solution is a function of the number 

of binding sites on the suspended particulate material. Extrapolating the toxicity-turbidity 

linear relationship would result in a predicted LC50 for rainbow trout of 7.3 mg/L at a 

turbidity of 1000 NTU and 18.3 mg/L at a turbidity of 3000 NTU, which would correspond 
Not to be released without written approval by NSS 25

to a toxic threshold for the most sensitive endpoint of 5.2 and 13.2 mg/L, respectively (Table 

13). 

For application of the product, WDOE requires a three-fold safety margin between the 

concentration of the product at discharge and the toxic threshold for the product (WDOE, 

2003). Thus, the data support application of Liqui-Floc at rates of 0.51, 0.68 and 1.08 mg/L 

in waters with turbidities of 50, 200 and 500 NTU with no further treatment necessary in 

order to maintain the safety margin. Based on an extrapolation of the dataset, predicted 

acceptable maximum application rates at 1000, 2000 and 3000 NTU would be 1.75, 3.07 

and 4.40 mg/L, respectively (Table 13). 

The application rates proposed here in order to meet the requirements of WDOE (2003) are 

based solely on Liqui-Floc treated turbid water without further treatment. The proposed 

Liqui-Floc treatment design incorporates a subsequent clean-up sand filtration step which 

has been shown to substantially remove residual dissolved chitosan, in addition to removing 

Liqui-Floc sorbed to particulate. Thus, the actual application of this product provides a 

significant further safety margin to the treatment system, well beyond that required by 

WDOE (2003).” 

Table 1 (in the report) Proposed acceptable application rates based on the toxicity-turbidity 

data for rainbow trout (50–500 NTU) and an extrapolation of the dataset (>500 NTU). 

Turbidity 

(NTU) 

Derived from: 96-hr trout 

LC50 

(mg/L) 

Toxic threshold 

IC25 

(mg/L) 

Maximum 

application rate* 

(mg/L) 

50 Data 2.11 1.52 0.51 

200 Data 2.83 2.03 0.68 

500 Data 4.52 3.25 1.08 

1000 Extrapolated 7.28 5.24 1.75 

2000 Extrapolated 12.82 9.22 3.07 

3000 Extrapolated 18.35 13.20 4.40 

*based on a three-fold safety margin relative to the toxic threshold. 

The Consultant notes that the three-fold safety margin was specified by Mr. Randy 

Marshall of the Department of Ecology (MacPherson, pers. comm.) 

In-situ field tests of treated discharge 

Tests were conducted at the Lakeside construction site where the CESF-FT system was 

employed (ECO-Endeavors, 2004). The full report is enclosed as Appendix H. Key 

excerpts from the report are presented below. 

Purpose: The purpose of this test is to determine if there is any chronic mortality to 

Rainbow trout continually exposed to stormwater treated by CESF. In-line test 

chambers will receive water after the polishing filter (the last stage of treatment) and 

prior to discharge from the site. 
Not to be released without written approval by NSS 26

Discussion: No mortality was observed at anytime during the 14-day screening in 

either the test or control chambers. Organisms appeared normal and actively fed. 

Days 10-14 had temperature readings over 20 ̊C, which is well above the 12 ̊C 

Whole Effluent Toxicity (WET) testing standard. With the increase in temperature, 

a marked drop in dissolved oxygen (DO) levels was observed. DO levels in the 

control chamber were below the 60 percent WET saturation level on days 10 and 11, 

58 and 57 percent, respectively. DO levels in the test chamber were below the 60 

percent WET saturation level on days 13 and 14, 58 and 56 percent, respectively. 

However, the organisms continued to actively feed and appeared normal despite the 

elevated temperatures and decreased DO levels. Such fluctuations would not be 

anticipated had the test been performed in the winter months when ambient 

temperatures are much lower. This situation was expected to occur as the test was 

started on June 8, 2002 when temperatures are warmer and was the reason the test 

was only run for 14-days. 

Despite the discrepancies with standard test temperature and DO levels, survival 

rates were 100% in both test and control chambers. 

Conclusion: From the data it appears that no chronic toxicity was observed after 14 

days of continuous exposure to stormwater treated by the Flow-through Chitosan 

Enhanced Sand Filtration process. 

MEETING THE DISCHARGE QUALITY SPECIFICATIONS 

Ecology’s specifications with regard to effluent quality are “achieve performance goals 

of a minimum of 95% reduction of NTU turbidity, a maximum discharge of 10 NTU 

turbidity, and a discharge pH within a range of 6.5-8.5. If these values are exceeded at 

any time the responsible site operating personnel shall immediately take appropriate 

corrective actions.” It is of interest to note that the new NDPES Construction Permit 

specifies a limit of 25 NTU for all construction sites, irrespective of the BMPs employed.

To meet the QAPP there has to be a minimum of 20 operating periods, and 480 influent 

and 480 effluent samples each for turbidity and pH for each site. These numbers have 

been exceeded at each site. The total number of operating periods at this time for the ten 

units at the three sites exceeds 1,500. The total number of data points exceeds 95,000 for 

each of the two effluent parameters. 

The Consultant examined selected data generated at the test sites. Generally, the above 

specifications were met. Provided below for each site are representative data. The entire 

data base is not presented given its enormity. Data for other time periods can be provided 

if requested. When examining the discharge graphs it is important to recognize that the 

discharge quality always meets the specifications. If it does not, the discharge from the 

filters is recycled to the holding basin. The frequency with which the discharge did not 

meet the discharge limits and was recycled at each site is discussed later in this report. 
Not to be released without written approval by NSS 27

Lakeside Housing Development 

Presented Figures 9 and 10 are discharge data for this site. The data are over one year, but 

recognize that operation is not continuous. They represent 65 operating periods and about 700 

individual data points for each discharge parameter. 

Lakeside Site Influent and Effluent Turbidity 

0

1

10

100

1000

1

March 2003 to March 2004

Turbidity (NTU)

Influent

Effluent

FIGURE 9 Influent and Effluent Turbidity 

Lakeside Site Effluent pH

6

6.5

7

7.5

8

8.5

1

March 2003 to March 2004

pH

FIGURE 10 Effluent pH 
Not to be released without written approval by NSS 28

SeaTac International Airport Third Runway 

Data from Unit Unit 4 (two systems in parallel) are provided for March through May 2005. 

During this period there were 24 operating periods and about 2,225 data points each for pH and 

turbidity. Figure 11 provides turbidity data and Figure 12 presents pH data. 

Sea Tac Airport Turbidity Reduction for March, April, May 2005 

Logarithmic Scale

0

1

10

100

1000

1

March, April, May 2005

Turbidity (NTU)

March Influent Turbidity

March Effluent Turbidity

April Influent Turbidity

April Effluent Turbidity

May Influent Turbidity

May Effluent Turbidity

FIGURE 11 Influent and Effluent Turbidity 

Sea Tac Airport Effluent pH Values

6.00

6.50

7.00

7.50

8.00

8.50

9.00

1

March, April, May 2005

pH

March Effluent pH

April Effluent pH

May Effluent pH

FIGURE 12 Effluent pH 
Not to be released without written approval by NSS 29

WSDOT SR-522 Road Improvement Project 

Data from the Echo Lake interchange facility are provided for period of March through May 

2005. Figures 13 and 14 provide turbidity data. Figure 13 presents data for the entire three 

months. Figure 14 provides the data only for May to further illustrate the high turbidity in the 

stormwater prior to pre-treatment as it entered the holding basin. Figure 15 presents pH data. The 

data represent 63 operating periods and about 4,200 points each for turbidity and pH. At this site 

the pH often rose above 8.5 due to algal activity in the holding basin. Liquid carbonic acid was 

used to lower the pH. 

WSDOT SR 522 Turbidity Reduction 

Logarithmic Scale

0

1

10

100

1000

1

March, April, May 2005

Turbidity (NTU)

March Influent Turbidity

March Effluent Turbidity

April Influent Turbidity

April Effluent Turbidity

May Influent Turbidity

May Effluent Turbidity

FIGURE 13 Influent and Effluent Turbidity 

WSDOT SR522 Turbidity 

1

10

100

1000

10000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

May 2005

Turbidity (NTU)

FIGURE 14 Turbidity 

Effluent

Before pretreatment 

Influent to filters 
Not to be released without written approval by NSS 30

WSDOT SR 522 Effluent pH Values

6.0

6.5

7.0

7.5

8.0

8.5

9.0

1

March, April, May 2005

Ph

March pH

April pH

May pH

FIGURE 15 Effluent pH 

RELIABILITY 

The data in Figures 9 through 15 indicate that the CESF-FT meets the effluent requirements with 

respect to pH and turbidity, with the inclusion of automatic recycle. Of particular relevance is the 

frequency in which the discharge quality does not meet the discharge requirements, either 

turbidity or pH. The Consultant requested NSS to evaluate this question for the SeaTac Airport 

and WSDOT sites. The Consultant examined the analysis and the data used in the analysis. 

Presented in Table 6 is the history of recycle for these two sites for the time period evaluated in 

Figures 11 through 15. 

TABLE 6 RECYCLE VOLUME HISTORY 

Month Seatac System Unit 4 WSDOT SR522 

March 4.9% 12.3% 

April 8.3% 12.8% 

May 6.8% 17% 

Both sites experiencing unusual site or system conditions, the later a reflection of new elements 

in the particular CESF-FT system. 

The recycle volume for Unit 4 at the SeaTac Airport site ranged from 17 to 27% during the first 

three months of operation (December 2004 through February 2005). The startup of Airport site 

was complex because of the number of systems involved, the short time frame within which the 

systems had to be installed, and the occurrence of an extreme storm event that nearly exceeded 

the total capacity of the treatment systems. The most serious mechanical problem was due to the 

internal corrosion of the chitosan storage tanks, which caused small pieces of corrosion debris to 
Not to be released without written approval by NSS 31

clog the chitosan metering pumps stopping the flow of the treatment agent. When the chitosan 

stopped flowing the treatment failed and the systems went into recycle mode while operators 

dismantled and cleaned the metering pumps. This problem was repeated frequently until the 

chitosan storage tanks were replaced with non-corrosive tanks. Once this problem was corrected 

the systems ran as designed and no further problems were encountered. 

The SR522 site reflected what may be the most extreme site conditions that the CESF-FT system 

will experience. Difficulties were faced throughout the treatment period, not just during startup. 

• The pH varied from 6.5 to 9.5 based due to the nature of site work and algal production in 

the holding basin. 

• The turbidity varied rapidly from nearly clean to above several thousands NTU. 

• The volume of water occasionally exceeded the system’s cpacity, particularly when the 

turbidity was very high. Pretreatment became a critical factor. 

The considerably higher recycle times on the WSDOT SR522 project reflect the fact that this 

difficult site required times where the system was intentionally put into recycle while dosing 

with chitosan in an effort to reduce the turbidity of the holding basin before treatment. Because 

of the nature of the project (linear highway project) there were times when the turbidity rose to 

thousands of NTU without warning. During these times the only way to reduce the turbidity was 

to recycle the water while adding chitosan. 

The Consultant noted during the field visit that while there is a flow meter on the discharge line, 

the data are not recorded. There is therefore no direct record that recycle occurs each time the 

discharge limits are not met. Rather, it is presumed that it occurs based on the records of the 

turbidity and pH, measured immediately in the discharge of the filter system, and the activation 

of the alarm system. The above calculations were made through the examination of the record 

on turbidity and pH. Where either or both parameters were outside the discharge specifications, it 

was presumed that recycle occurred. Since recycle occurs automatically, it can only be presumed 

that the recycle valve functioned satisfactorily in all instances. For this reason, the Consultant has 

recommended that the discharge flow be recorded. 

FACTORS OTHER THAN PERFORMANCE 

Discussion of factors 

This aspect of the TAPE protocol is presented in a table format in Table 7 with responses to each 

item listed in the protocol. Costs are discussed separately from the table, following the table. 
Not to be released without written approval by NSS 

TABLE 7 SUMMARY DISCUSSION OF OTHER FACTORS 

FACTOR DISCUS

TECHNOLOGY DESCRIPTIONDescribe the treatment technology including process diagrams, primary equipment drawings, sketches, etc. Include details on the relevant treatment mechanisms such as: Filter media grain size distribution, clean media hydraulic conductivity, hydraulic conductivity versus sediment loading (provide sediment grain size distribution and dry density used in analysis), provide typical and maximum operational hydraulic gradient. 

See Page 9. Hydraulic gradients are as it is a pumped system. 

APPLICATIONS For which applications (e.g., land uses such as roadways, high-use sites, commercial, industrial, residential runoff areas) does the vendor recommend this technology. 

There are no inherent factors limiting applicable to all construction sites of 

What are the pretreatment requirements. Treat when influent to holding pond 

efforts at effective source control. 

Provide a list of the facilities that are installed in the United States. Include addresses and size of each facility. Provide at least three references with names and telephone numbers. 

The CESF-FT system has or is being wiith about 50 are in Washington. A NSS is not involved at all sites. Site oLakeside Larry Darnell, (425)-313-2Thorwart (253)831-7102; SR522, W

SITE CHARACTERISTICS Do any site characteristics or safety considerations favor or limit the technology’s use: climate, rainfall, steep slopes, high groundwater, seepage/baseflows, tidal action, soil type including organics and pH, proximity to wells, septic systems and buildings, facility depth limits for access and safety, hazardous materials spill risk, driving head requirements, and power. 

There are no inherent factors limiting potentially applicable for all construccharacteristics and acreage. 

DESIGN CRITERIA FOR SIZING Pollutant removal at design flow and for representative stormwater characteristics. See discussion beginning on Page 26Design hydraulics (design flow and/or volume, by-pass flow, hydraulic grade line, scour velocities, etc.). 

Design flow rate is set by the dischargradients are meaningless as it is a pu

Design residence time, vertical/horizontal velocities, etc. Residence time in the filters is about Stormwater constituent limitations (pollutants and other constituents), fouling factors. None, as pretreatment addresses the iSpecific media flow rate (design velocity). Operate at less than 15 GPM/ft2 of filMedia head loss curves. This relationship has not been develo

the tests and variable conditions betw
Not to be released without written approval by NSS 

TABLE 7 SUMMARY DISCUSSION OF OTHER FACTORS (continued) 

FACTOR DISCUSS

Minimum media contact time and minimum thickness. Contact time is about one minute. FiEstimate system/system components design life before major overhaul. Components receive overhaul as needMedia specifications ensuring adequate media quality at all times. A physical/chemical and impurity specifications list should be provided. 

See Page 11. Impurity specifications sand media as it meets a specific grad

CONSTRUCTION What role does the vendor take in design and construction. NSS provides the polymer, training, 

is the responsibility of the operator w

vendor of the equipment to design an

How is the technology installed. How long does it take. Standard construction procedures. En

installed within a few days to two we

How are factors such as structural integrity, water tightness, and buoyancy addressed. “Off-the shelf” equipment with years What types of problems can occur/have occurred in designing and installing the technology. None. System components are well eHow are potential problems diagnosed and corrected, and by whom. Monitoring of turbidity, pH, and filte

Problems are corrected by the site op

If problems go uncorrected, how does this affect the technology’s effectiveness. NA. Operator on site at all times. If p

system is shut down. Holding pond s

How available is the technology (e.g., where do the major components come from and how much lead time is needed). 

“Off-the-shelf” equipment is used anissue. Replacement parts are availabl

COSTS ... See Page 40.OPERATION AND MAINTENANCE Describe the level of training personnel shall have to operate and maintain the technology? Who provides the training, is a certification available. 

NSS provides training. Each operator training for one year before being cer

Describe how operation and maintenance personnel are supervised. By immediate superior who conducts How are inspections performed and how often. By operator. Occurs essentially contiHow do you tell know when maintenance will be needed, i.e., what is the "trigger." When the frequency of filter backwaHow is maintenance performed. Standard industrial procedures for eaAre all maintenance areas accessible by people and equipment. Are special equipment or methods needed for access? Any confined space entry areas. 

Yes, no confined space entry. 
TABLE 7 SUMMARY DISCUSSION OF OTHER FACTORS (continued) 

FACTOR DISCUSS

What is the estimated maintenance frequency and on what information/tests do you base this estimated maintenance frequency. 

Varies with each component. pH and 

each operating period and twice annu

What maintenance equipment and materials are required. System element is disassembled and Does the vendor offer a maintenance service contract? If so, provide cost information, including mobilization, equipment rental, mileage, solids/spent media disposal, etc. 

Maintenance is the responsibility of t

provider of the equipment, not NSS. 

How are solids/spent media classified (waste type) and disposed. Inorganic sediment. Disposed to the cCan the technology be damaged due to delayed maintenance, and if so, how is it restored. Excessive loading and failure to prop

total clogging of the sand, requiring r

How many years have you been in business? If vendor goes out of business or product model changes, how/where will facility owner find needed parts, materials, and service. 

Vendors, not NSS, provides equipmefor other applications, are readily ava

RELIABILITY What factors can cause the technology to not perform as designed. High influent turbidity, runoff of somCan the technology add, transform, or release accumulated pollutants. The system may discharge residual c

been observed above the detection lim

Is the technology sensitive to heavy or fine sediment loadings—is pretreatment required. Yes, as indicated in this report. How is underperformance diagnosed and treated. Monitoring of effluent pH and turbidWhat is the warranty. Provider of equipment provides the wWhat initial/ongoing user support is provided. Does the vendor charge for support. NSS gives technical advice if request

responsible for advising site contract

ROBUSTNESS How sensitive is the technology’s performance to not being maintained correctly. Sensitive. How are problems diagnosed and treated. Monitoring of effluent pH and turbid

tial; frequency of automatic backwas

Are system components durable, expected to last a reasonable length of time before repair. Yes OTHER FACTORS Does the technology provide benefits or present challenges in other ...areas, such as groundwater recharge, thermal effects, habitat creation, aesthetics, vectors, safety, community acceptance, recreational use, and efficacy on redevelopment sites. 

The technology is used only temporaaspects do not apply. 
Not to be released without written approval by NSS 35

Cost 

The TAPE (Ecology, 2003a) asks for the following information. 

• Installation-removal, operation and Lease (if applicable) costs: Base the cost analysis on 

the test results. 

• Indicate approximate seasonal system capital/operating costs for flow-through system 

models on a “design cfs treated basis” (not per cfs hydraulic capacity), or a dollar per 

TSS removed and/or turbidity reduced basis, using typical stormwater TSS 

concentrations (see earlier footnote). Batch treatment costs should be determined based 

on volume treated, gallon or cubic foot. 

The following is an analysis of the fixed and variable costs associated with operating a 

chitosan-enhanced sand filtration system including pretreatment. All assumptions are 

listed. The cost analysis was prepared by Natural Site Solutions. 

Assumptions for a 240,000 gallon per day facility 

Sand Filter (48” dia., 4-pod system) $3,000/month 

Sand (#30 grade crushed silica) + under rock $1,000/once only 

Mobilization cost $500/once only 

Demobilization cost $500/once only 

Chitosan $9.00/10,000 gallons treated at 1 ppm 

 $27.00/10,000 gallons treated at 3 ppm 

Diesel cost $1.75 per gal with an average consumption of 6 gph

20,000-gal pretreatment tank $900/month 

Mobilization cost $500/once only 

Demobilization cost $500/once only 

Pumps (2- 30 HP electric submersible w/ float level controllers, combined cost) $2,400/month 

Secondary metering pump for pretreatment $1,000/once only 

Controller Module (Brain Box) $3,500/month 

Mobilization/Demobilization $500/once only 

100 KVA Generator (diesel powered) $2,000/month 

System assembly (40 hours @ $50/hr) $2,000/once only 

System disassembly (20 hours @ $50/hr) $1,000/once only 

System operator $65/hr 

System performance data monitoring and reporting costs 20 hrs/month @$75 $1,500/month 

Once only costs excluding site preparation 

Sand Filter 

 Mobilization cost + sand filling $1000 

 Demobilization cost $500 

Pretreatment Tank 

 Mobilization cost $500 

 Demobilization cost $500 

Secondary metering pump for pretreatment $1,000 

Controller Module (Brain Box) 

 Mobilization/Demobilization $500 

System assembly (40 hours @ $50/hr) $2,000 

System disassembly (20 hours @ $50/hr) $1,000

 Total $7,000 
Not to be released without written approval by NSS 36

Reoccurring Monthly Costs 

Sand Filter (48” dia., 4-pod system auto backwash 400 gpm output) $3,000 

20,000-gal pretreatment tank $900 

Pumps (2- 30 HP electric submersible w/ float level controllers) $2,400 

100 KVA Generator (diesel powered) $2,000 

Controller Module (Brain Box) $3,500 

Removal and disposal of sediments from settling cell 20 hrs @$150/hr plus fee $3,500 

System performance data monitoring and reporting costs 20 hrs/mo @$75 $1,500

 Total $16,300 

Estimating Total Monthly System Costs for Three Scenarios 

The cost to treat is directly related to the quantity of water treated. Three scenarios are 

provided in Table 8, differing by the level of use. 

• Light use: defined as operating the system for four hours per day for ten days per 

month (total 960,000 gallons treated per month) 

• Moderate use: defined as operating the system six hours per day 15 days per 

month (total 2,160,000 gallons treated per month) 

• Heavy use: defined as operating the system ten hours per day 20 day per month 

(total 4,800,000 gallons treated per month) 

As an average assumption a chitosan acetate dose rate at 2 mg/L is used, 1.5 mg/L for 

pretreatment and 0.5 mg/L for filtration. Heavy use is most often associated with 

continuous dewatering activities, dredging, and unusually heavy and prolonged periods of 

precipitation. 

TABLE 8 THREE COST SCENARIOS 

Scenario One - Light use 

Variable Cost Element Duration Cost 

Operating Labor @ $65/hr Reasonably expect 50 hours $3,250

Fuel consumption (diesel) 40 hours @ 6 gph $420

Chitosan consumption 2 mg/L based on previous assumption $1,760

System performance data monitoring 

and reporting 

10 hrs/mo @$75 $750

Senior operator project oversight Assume 2 site visits (1 hour each)@$120/hr $240

Meeting with regulatory personnel 2 hours @ $120.hr $240

 Total Variable Costs $6,660

 Hard Cost Elements $13,300

 Total Hard & Variable Costs $19,960

Total cost of $19,960.00 divided by the amount of water treated gives a cost per gallon of $0.021. 
Not to be released without written approval by NSS 37

TABLE 8 (Continued) 

Scenario Two – moderate use 

Variable Cost Element Duration Cost 

Operating Labor @ $65/hr Reasonably expect 105 hours $6825

Fuel consumption (diesel) 90 hours @ 6 gph $945

Chitosan consumption 2 mg/L based on previous assumption $3,956

System performance data monitoring 

and reporting 

15 hrs/mo @$75 $1,125

Senior operator project oversight Assume 2 site visits (1 hour each)@$120/hr $240

Meeting with regulatory personnel 2 hours @ $120.hr $240

 Total Variable Costs $13,331

 Hard Cost Elements $13,300

 Total Hard & Variable Costs $26,631

Total cost of $26,631.00 divided by the total amount of water treated gives a cost per gallon of $0.012. 

Scenario Three - Heavy use 

Variable Cost Element Duration Cost 

Operating Labor @ $65/hr Reasonably expect 240 hours $15,600

Fuel consumption (diesel) 200 hours @ 6 gph $2,100

Chitosan consumption 2 mg/L based on previous assumption $8,800

System performance data monitoring 

and reporting 

20 hrs/mo @$75 $1,500

Senior operator project oversight Assume 4 site visits (2 hour each)@$120/hr $960

Meeting with regulatory personnel 2 hours @ $120.hr $240

 Total Variable Costs $28,984

 Hard Cost Elements $13,300

 Total Hard & Variable Costs $42,284

Total cost of $42,284.00 divided by the total amount of water treated gives a cost per gallon of water 

$0.009. 

REFERENCES 

AMTEST, 2005, Residual chitosan test procedure. 

ECO-Endeavors, 2004 (June 2), Rainbow trout (Oncorhynchus mykiss) Chronic Toxicity 

Screening of Stormwater Treated by Chitosan Enhanced Sand Filtration Flow-Through 

System-Redmond, Washington, for Natural Site Solutions, Redmond, Washington. 

Ecology, 2001, Stormwater Management Manual for western Washington. 

Ecology (Department), 2003a (September), Guidance for Evaluating Emerging 

Stormwater Treatment Technologies at Construction Sites, Chemical Technology 

Assessment Protocol – Ecology (CTAPE), Olympia, Washington. 

Ecology (Department), 2003b (October 27), Engineering Summary, Use Designations 

For Chitosan-Enhanced Sand Filtration, Olympia, Washington. 
Not to be released without written approval by NSS 38

Ecology (Department), 2004 (February 26, updated August 18), Engineering Summary, 

Use Designations For Chitosan-Enhanced Sand Filtration, Olympia, Washington. 

MacPherson, J., 2005, personal communication. 

MacPherson, J., 2006, memo to Consultant on chitosan pretreatment, February 27, 2006. 

Minton, G.R., and A. Benedict, 1999, Polymer-assisted clarification of stormwater from 

construction sites, Resource Planning Associates, for the City of Redmond, Washington. 

Natural Site Solutions, LLC (NSS), 2003, Chitosan-Enhanced Sand Filtration System – 

Operation and Maintenance Manual, Redmond, Washington. 

NSS, 2004a (January 12), Quality Assurance Project Plan, Chitosan-Enhanced Sand 

Filtration, Redmond, Washington. 

NSS, 2004b (June 24), Application for General Use Designation: Chitosan-Enhanced 

Sand Filtration Stormwater Treatment Technology, Redmond, Washington. 

Nautilus Environmental LLC, 2004 (September 30), Toxicity testing for Liqui-Floc, Final 

Report, for Natural Site Solutions, Redmond, Washington. 
Not to be released without written approval by NSS 39

APPENDIX A 

RECOMMENDED SPECIFICATIONS FOR PERMITTED FACILITIES 

CHITOSAN-ENHANCED SAND FILTRATION TECHNOLOGY 

FOR FLOW-THROUGH OPERATIONS

The following specifications identify elements of the SWPPP for each construction site. 

1. Stormwater discharges from the CESF-FT system shall not cause or contribute to 

receiving surface water quality violations. 

2. If the discharge from the CESF-FT system will be to a fish spawning area in the stream 

an approval for that discharge must be obtained from the responsible Ecology Regional 

Office. 

3. The CESF-FT facility contractor shall guarantee that CESF-FT system, when used as 

directed, will not produce treated water which exhibits aquatic toxicity caused by 

chitosan added as a treatment agent. 

4. The CESF-FT system shall only be operated by a trained technician certified through an 

approved training program that includes classroom and field instruction. Training to be 

provided by a qualified trainer. The technician shall have the following Minimum 

Training Requirements. 

• Minimum 1-year experience with, and sound working knowledge of, high 

pressure sand filter systems. 

• Experience deploying and troubleshooting pressurized water pumping and piping 

systems. 

• Fundamental knowledge of stormwater discharge regulations for applicable 

region/locale. 

• Fundamental knowledge of stormwater quality testing procedures and methods 

for parameters applicable to the region/locale.(note: class and field content is 

specified but not included here) 

5. The facility shall employ a minimum of three (3) sand filter pods to ensure adequate 

backwashing capacity. The backwash slurry from the sand filters must be discharged to a 

holding cell that is separate from the temporary storage cell for the incoming turbid 

stormwater. The overflow from the backwash slurry holding cell can overflow into the 

holding basin for the turbid stormwater. 

6. The operating flow rate shall not exceed 15 GPM per square foot of sand bed filtration 

area. 

7. The filtration media shall be pre-washed #30 crushed silica sand with a mean effective 

sand size of 0.34 mm and a filtration quality mesh of 230-400. Minimum sand bed depth 

shall be 18-inches underlain with a minimum of 6-inches of 1-inch crushed rock. 

8. The CESF-FT system shall include a flow-regulating valve on the input to and output of 

the sand filter. These regulating valves will reduce the maximum output of the pump as 

required and facilitate proper backwash. 
Not to be released without written approval by NSS 40

9. Water quality influent and effluent shall be continuously monitored and recorded for 

flow, pH and turbidity. 

10. The CESF-FT system treated water output shall be equipped with an automatic integrated 

turbidity and pH sensors capable of shutting the system down if output turbidity or pH 

exceed preset values. An audible alarm and warning light shall be installed on the 

treatment system to alert the operator in the event of a system failure. 

11. The discharge flow rate shall be metered and recorded. 

12. The CESF-FT control system (including metering pump, chitosan storage and 

instrumentation) shall be completely enclosed in a secure structure with locking door. 

The chitosan liquid concentrate tank, metering pump and tubing shall have secondary 

containment. The metering pump discharge tubing shall have an anti-siphon valve. 

13. Chitosan injection shall be performed with an LMI-brand C77, high viscosity pump head, 

electric metering pump, or equivalent. The metering pump must be calibrated within 15 

minutes of the beginning of each operating period. It is to be recalibrated when a 

significant change occurs in either flow or influent turbidity. 

14. The maximum suspended sediment (expressed as turbidity) of the influent water entering 

the holding basin(s) should not exceed 600 NTU. Source control procedures shall be 

implemented to the maximum extent feasible to minimize the need for the use of chitosan 

acetate for the pretreatment of stormwater entering the holding basin. 

15. The chitosan acetate dose rate for water entering the filters shall not exceed 1 mg/L (as 

chitosan acetate by weight). All calibration results must be recorded simultaneously with 

the flow rates and the records kept on site. • 

16. A variance can be sought to use additional chitosan acetate for pretreatment of 

stormwater entering the holding basin. It shall be demonstrated, however, that source 

control BMPs are unable to meet the pretreatment requirement of 600 NTU. 

17. Only those forms of chitosan acetate approved by the Department of Ecology shall be 

used. 

18. Jar tests will be conducted, as needed, to confirm the dosage level of chitosan acetate. 

19. The SWPPP is to include a field procedure, accepted by the Department of Ecology, for 

detecting a residual of chitosan in the discharge, sensitive to 0.2 mg/L. 

20. .The discharge from the sand filters shall be maintained below 0.2 ppm residual chitosan 

at all times. A discrete grab sample of a homogeneous sand filter discharge must be 

collected and analyzed within 30 minutes of the onset of operation. The test is to be 

repeated whenever there is a change in dosage, or a significant change in influent 

turbidity of flow rate. 

21. An operation and maintenance manual shall be prepared and available on-site. 

22. A contingency plan to immediately correct the problem must be included in each SWPPP 

and Operation and Maintenance manual in the event that the above specified residual 

chitosan is exceeded, exhibits aquatic toxicity based on approved bioassay testing, or 

when the CESF system fails to meet discharge quality requirements. 

23. During the planning (SWPPP preparation, etc.) of a project the adverse potential impact 

on chitosan efficiency of the use of anionic polymers for soil blanketing and stability, 

will be evaluated. 
Not to be released without written approval by NSS 41

24. An Operating Period Information Form shall be completed for each operating period. 

The recommended format is included with these specifications. At a minimum, the form 

shall include the following information. 

• A record of each recycle event 

• A record of each backwash event 

• Actions taken when a recycle event occurs 

• Actions taken when excessive backwashing is occurring 

• A record of pump calibration 

• A record of chitosan use for pretreatment 

• A record of chitosan dosage immediately prior to the filters 

• A record of test results for chitosan residual in the effluent 

The supervisor of the operator shall examine weekly the forms completed the previous 

week. The supervisor shall sign each daily form indicating it has been reviewed, and also 

document actions he or she has taken in response to any abnormal conditions observed by 

the operator. 

25. At all construction sites, at the end of each operating period, a delegated responsible 

person shall record his/her assessment of the operational efficiency of the CESF process 

and all upsets, the sand filter discharge chitosan concentrations and any other relevant 

observations that relate to CESF proper operation and must also certify the acceptability 

of the CESF discharge to surface water. 

26. These stipulations supersede BMP C-250. 
Not to be released without written approval by NSS 42

APPENDIX B OPERATING PERIOD INFORMATION FORM 

CESF Treatment System Shift Log

Treatment Unit Startup Time 

 Date Startup Totalizer 

Operator #1 Startup Flowrate 

Operator #2 

Operator #3 Shutdown Time 

Shutdown Totalizer 

Total Gallons Treated 

Initial System Checkout 

Chitosan Polymer 

Level 

F 3⁄4 1⁄2 1⁄4 

General System 

Integrity 

Grab Sample Confidence Checks 

Influent Turbidity = Influent Turbidity 

Influent pH = Influent pH 

Effluent Turbidity = Effluent Turbidity 

Effluent pH = Effluent pH 

 pH & Turbidity Reading from Controller (4 sample measurements per shift1

) 

#1 Time: #2 Time: #3 Time #4 Time: 

pH 

Turbidity (NTU) 

Residual Chitosan Test (15 min. & 4 hours after startup) 

Time Result - positive (>0.2 mg/L) / negative (<0.2 mg/L) 

Sample #1 

Sample #2 

Backwash Settings: Default time interval (minutes) Differential pressure 

(psid) 

Starup: 

If changed: 

If changed: 

Notes/Observations: 

Did recycle occur because the discharge quality did not meet discharge requirements? Give time, 

duration and corrective action:

Operator comments: Acceptable / Unacceptable (circle one) 

Operator Signature: 

 

1

 For reporting purposes 4 pH and turbidity readings are needed per day. Because only one shift may be run, 4 

readings are needed each shift. The pH and turbidity readings may be taken directly from the digital 

readout on the Hach controllers. 
Not to be released without written approval by NSS 43

APPENDIX C EXAMPLES OF COMPLETED DAILY LOG FORMS 
Not to be released without written approval by NSS 44
Not to be released without written approval by NSS 45