Mission Creek Watershed DDT 

Total Maximum Daily Load 

Water Quality Improvement Report 

July 2007 

Publication Number 07-10-046 

 

Mission Creek Watershed DDT 

Total Maximum Daily Load 

Water Quality Improvement Report

Prepared by: 

Ryan Anderson 

Washington State Department of Ecology 

Water Quality Program 

July 2007 

Publication Number 07-10-046 
You can print or download this document from our Web site at: 

http://www.ecy.wa.gov/biblio/0710046.html

For more information contact: 

Department of Ecology 

Water Quality Program 

Central Regional Office 

15 W Yakima Ave, Suite 200 

Yakima, WA. 98902-3401 

Telephone: 509-454-7844 

Adams

Benton Asotin

Chelan

Clallam

Clark

Columbia

Cowlitz

Douglas

Ferry

Franklin Garfield

Grant

Grays

Harbor

Island

Jefferson

King

Kitsap

Kittitas

Klickitat

ic Lewis

Lincoln

Mason

Okanogan

Pacif

Pend

Oreille

Pierce

San Juan

Skamania

Spokane

Stevens

Thurston

Skagit

Snohomish

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Walla

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akum Yakima

Northwest

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Southwest

360-407-6300

Eastern

509-329-3400

Central

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Headquarters (Lacey) 360-407-6000

Regional

Office

location

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Persons with a speech disability can call 877-833-6341.

If you need this publication in an alternate format, please call the Water Quality Program at 

509-454-7844. Persons with hearing loss can call 711 for Washington Relay Service. Persons 

with a speech disability can call 877-833-6341
Table of Contents 

List of Figures................................................................................................................................. ii 

List of Tables.................................................................................................................................. ii 

Executive Summary.......................................................................................................................iii 

Acknowledgements......................................................................................................................... v 

Introduction..................................................................................................................................... 1 

TMDL Process Overview ............................................................................................................... 3 

Elements required in a TMDL..................................................................................................................3

Background...............................................................................................................................................4

Applicable water quality criteria ..............................................................................................................6

Human health criteria ...............................................................................................................................6

Water quality and resource impairments..................................................................................................7

Seasonal variation.....................................................................................................................................7

Stormwater ...............................................................................................................................................8

Technical Analysis.......................................................................................................................... 9 

Study design .............................................................................................................................................9

Sample locations.......................................................................................................................................9

Data analysis...........................................................................................................................................11

Results....................................................................................................................................................12

DDT concentrations in surface water and shallow ground water...........................................................12

Loading Capacity and Load Allocations....................................................................................... 17 

Total DDT targets...................................................................................................................................17

Margin of safety .....................................................................................................................................18

Summary Implementation Strategy .............................................................................................. 21 

Implementation overview.......................................................................................................................21

Implementation plan development .........................................................................................................21

Implementation activities .......................................................................................................................21

Implementation activities table...............................................................................................................22

Reasonable assurances............................................................................................................................24

Adaptive management............................................................................................................................24

Monitoring strategy ................................................................................................................................24

Potential Funding Sources............................................................................................................ 26 

References Cited ........................................................................................................................... 27 

Appendix A................................................................................................................................... 29 

Appendix B................................................................................................................................... 31 

Mission Creek Watershed DDT TMDL Page i 

Water Quality Improvement Report 
List of Figures 

Figure 1: Map of the Mission Creek Watershed including Yaksum Creek and Brender Creek... 4 

Figure 2: Stream flow in liters/Second (l/s) for Mission Creek at Cashmere................................ 5 

Figure 3: Map of the project area with sampling locations for surface water and sediment sample 

site locations................................................................................................................. 10 

Figure 4: Soil sampling site locations for the technical report. ................................................... 11 

List of Tables 

Table ES-1: 303(d) listings in the Mission Creek Watershed addressed by this TMDL..............iii 

Table ES-2: t-DDT load reductions presented by this TMDL....................................................... iv 

Table 1: Water quality criteria to protect aquatic life and human health from DDT and its 

breakdown products. ....................................................................................................... 6 

Table 2: Mission Creek Watershed waterbodies on the 2004 303(d) List for DDT, DDE, and 

DDD................................................................................................................................. 7 

Table 3: Conventional parameters in surface water and shallow ground water. ......................... 13 

Table 4: Concentrations of DDT (ng/l) in surface water and shallow ground water................... 15 

Table 5: Load reductions required to meet target t-DDT loads in Mission, Brender, and Yaksum 

Creeks. ........................................................................................................................... 17 

Table 6: Organization of TMDL entities and their contributions. (A list of acronyms is provided 

at the end of the table). .................................................................................................. 23 

Page ii Mission Creek Watershed DDT TMDL 

Water Quality Improvement Report 
Executive Summary 

The federal Clean Water Act requires that a total maximum daily load (TMDL) be developed for 

each of the waterbodies on the 303(d) list. The TMDL identifies pollution problems in the 

watershed, and then specifies how much pollution needs to be reduced or eliminated to achieve 

clean water. The Washington State Department of Ecology (Ecology) then works with the local 

community to develop, (1) an overall approach to control the pollution, called the summary 

implementation strategy, and (2) a monitoring plan to assess the effectiveness of the water 

quality improvement activities. 

Ecology conducted this TMDL in order to set targets that, if achieved, will bring 303(d) listed 

streams in the Mission Creek watershed into compliance with state water quality standards. 

Table ES-1 shows the 303(d) listed streams in the watershed addressed by this TMDL. 

Table ES-1: 303(d) Listings in the Mission Creek Watershed addressed by this TMDL. 

Waterbody Parameter Medium Listing ID 

Township 

Range 

Section 

Mission Creek 4,4’-DDD Water 34832 23N 19E 04 

Mission Creek 4,4’-DDE Water 34826 23N 14E 04 

Mission Creek 4,4’-DDE Fish Tissue 8960 23N 19E 04 

Mission Creek 4,4’-DDT Water 34829 23N 19E 04 

Mission Creek 4,4’-DDT Water 8958 23N 19E 04 

Mission Creek 4,4’-DDT Fish Tissue 8959 23N 19E 04 

Brender Creek 4,4’-DDD Water 34833 23N 19E 05 

Brender Creek 4,4’-DDE Water 34827 23N 19E 05 

Brender Creek 4,4’-DDT Water 34830 23N 19E 05 

Yaksum Creek 4,4’-DDD Water 34834 23N 19E 09 

Yaksum Creek 4,4’-DDE Water 34828 23N 19E 09 

Yaksum Creek 4,4’-DDT Water 34831 23N 19E 09 

The Mission Creek watershed is in Water Resource Inventory Area (WRIA) 45 which is also 

known as the Wenatchee River watershed. The watershed is in Chelan County in central 

Washington State. The Mission Creek watershed drains 93.3 square miles (59,712 acres), from 

the Wenatchee National Forest uplands to the Wenatchee River at the city of Cashmere, 

Washington. 

Brender Creek, Yaksum Creek, and No Name Creek are tributaries to Mission Creek. The 

climate is characterized by mild to severe winters with hot, dry summers. Streams in the 

watershed have high flows following snowmelt in the spring and early summer. 

The water quality standard for DDT and DDE in water is 0.59 ng/l and is 0.83 ng/l for DDD. 

One ng/l equals one part per trillion (ppt). The study found that total-DDT concentrations in 

Mission Creek Watershed DDT TMDL Page iii 

Water Quality Improvement Report 
filtered and unfiltered surface water ranged from 0.1 ng/l to 130 ng/l t-DDT at all sites except in 

Mission Creek above the Wenatchee National Forest boundary. 

The highest t-DDT concentrations were found in lower Yaksum Creek. In order to meet water 

quality standards, load reductions of t-DDT need to meet the targets presented in table ES-2. 

Table ES-2: t-DDT load reductions presented by this TMDL 

Stream/Location 

Harmonic 

Mean 

Discharge 

(l/s) 

t-DDT 

Criterion 

(ng/l) 

Target 

Load 

(mg/d) 

Average 

t-DDT 

(ng/l) 

Current 

Load 

(mg/d) 

Load 

Reduction 

(mg/d) 

Load 

Reduction 

(%) 

Mission Creek – 2MC 138 1 12 3.2 38 26 69 

Mission Creek – MISSPZ1 97 1 8.4 0.4 3.4 (5.0) (150) 

Brender Creek – 3MC 86 1 7.4 11 84 77 91 

Brender Creek – BRENPZ1 37 1 3.2 26 83 80 96 

Yaksum Creek – near mouth 18 1 1.6 62 96 94 98 

( ) = reserve capacity 

The TMDL recommendations will be carried out through existing requirements and programs, as 

well as voluntary measures to reduce soil erosion in Mission Creek watershed and education. 

Monitoring will measure progress toward water quality goals. A water quality implementation 

plan will be developed within a year after the United States Environmental Protection Agency 

approves this TMDL. 

Page iv Mission Creek Watershed DDT TMDL 

Water Quality Improvement Report 
Acknowledgements 

Many thanks to the participants on the Wenatchee Water Quality Technical Subcommittee and 

Wenatchee Watershed Planning Unit for their ongoing participation, technical support, wise 

suggestions, dedication, and commitment to improving water quality and the environment. The 

Mission Creek Watershed DDT TMDL was developed through the participation and input of 

numerous stakeholders from the Wenatchee Watershed over several years, many of whom spent 

countless hours providing information, reviewing and formulating plan actions, and attending 

meetings to represent their constituencies. 

Mission Creek Watershed DDT TMDL Page v 

Water Quality Improvement Report 
Page vi Mission Creek Watershed DDT TMDL 

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Introduction 

The Clean Water Act established a process to identify and clean up polluted waters. Under the 

Clean Water Act, each state is required to have its own water quality standards designed to 

protect, restore, and preserve water quality. Water quality standards consist of designated uses 

for protection, such as cold water biota and drinking water supply, as well as criteria (usually 

numeric criteria) to achieve those uses. 

Every two years, states are required to prepare a list of waterbodies – lakes, rivers, streams, or 

marine waters – that do not meet water quality standards. This list is called the 303(d) list. To 

develop the list, the Department of Ecology (Ecology) compiles its own water quality data along 

with data submitted by local, state, and federal governments, tribes, industries, and citizen 

monitoring groups. All data are reviewed to ensure that they were collected using appropriate 

scientific methods before it is used to develop the 303(d) list. The 303(d) list is part of the larger 

Water Quality Assessment. 

The Water Quality Assessment is a list that tells a more complete story about the condition of 

Washington’s water. This list divides waterbodies into one of five categories: 

Category 1 – Meets standards for parameter(s) for which it has been tested 

Category 2 – Waters of concern 

Category 3 – Waters with no data available 

Category 4 – Polluted waters that do not require a Total Maximum Daily Load (TMDL) 

because: 

4a. – Has a TMDL approved and it is being implemented 

4b. – Has a pollution control program in place that should solve the problem 

4c. – Is impaired by a non-pollutant such as low water flow, dams, culverts 

Category 5 – Polluted waters that require a TMDL – the 303d list. 

Washington’s 303(d) list consists of those waterbodies that fall into Category 5 in the Water 

Quality Assessment process. 

Mission Creek Watershed DDT TMDL Page 1 

Water Quality Improvement Report 
Page 2 Mission Creek Watershed DDT TMDL 

Water Quality Improvement Report 
TMDL Process Overview 

The Clean Water Act requires that a TMDL be developed for each of the waterbodies on the 

303(d) list. The TMDL identifies pollution problems in the watershed and then specifies how 

much pollution needs to be reduced or eliminated to achieve clean water. Then Ecology works 

with the local community to develop an overall approach to control the pollution, called the 

summary implementation strategy, and a monitoring plan to assess effectiveness of the water 

quality improvement activities. Once the United States Environmental Protection Agency (EPA) 

approves the TMDL, a water quality implementation plan (WQIP) should be developed within 

one year. The WQIP identifies specific tasks, responsible parties and timelines for achieving 

clean water. 

This TMDL submittal is based on work presented in DDT Contamination and Transport in the 

Lower Mission Creek Basin, Chelan County (Serdar and Era Miller, 2004) which will be referred 

to as the technical report. 

Elements required in a TMDL 

The goal of a TMDL is to ensure the impaired water will attain water quality standards. A 

TMDL includes a written, quantitative assessment of water quality problems and of the pollutant 

sources that cause the problem. The TMDL determines the amount of a given pollutant that can 

be discharged to the waterbody and still meet standards (the loading capacity) and allocates that 

load among the various sources. This allocation was published in the technical report. The 

Wenatchee Watershed Planning Unit’s (WWPU) Water Quality Technical Subcommittee 

(WQTS) reviewed the technical report twice. 

If the pollutant comes from a discrete source (referred to as a point source) such as a municipal 

or industrial facility’s discharge pipe, that facility’s share of the loading capacity is called a 

wasteload allocation. If the pollutant comes from a diffuse source (referred to as a nonpoint 

source) such as urban, residential or farm runoff, the cumulative share of diffuse source inputs is 

called a load allocation. 

The TMDL must also consider seasonal variations and include a margin of safety that takes into 

account any lack of knowledge about the causes of the water quality problem or its loading 

capacity. A reserve capacity for future loads from growth pressures may be included. The sum 

of the wasteload and load allocations, the margin of safety, and any reserve capacity must be 

equal to or less than the loading capacity. 

Identifying the contaminant loading capacity for a waterbody is an important step in developing 

a TMDL. EPA defines the loading capacity as “the greatest amount of loading that a waterbody 

can receive without violating water quality standards” (EPA, 2001). The loading capacity 

provides a reference for calculating the amount of pollution reduction needed to bring a 

waterbody into compliance with standards. The portion of the receiving water’s loading capacity 

assigned to a particular source is a load allocation (LA) or wasteload allocation (WLA). By 

definition, a TMDL is the sum of the allocations, which must not exceed the loading capacity. 

Mission Creek Watershed DDT TMDL Page 3 

Water Quality Improvement Report 
TMDL = loading capacity = sum of all WLAs + sum of all LAs + margin of safety 

This TMDL does not present WLAs because there are no point sources in the Mission Creek 

watershed that contribute dichloro-diphenyl-trichloroethane (4,4’-DDT) or its breakdown 

products, dichloro-diphenyl-dichloroethane (4,4’-DDD) and dichlor-diphenyl-ethane (4,4’-

DDE). 

In this TMDL, 4,4’-DDT, 4,4’-DDD, and 4,4’-DDE are referred to as DDT, DDD, and DDE. 

The result of adding the concentrations of DDT, DDD, and DDE is referred to as total DDT (tDDT). 

Background 

The Mission Creek watershed is located within the Wenatchee River watershed (WRIA 45) in 

Chelan County near the central part of the state of Washington (State). The Mission Creek 

watershed drains 93.3 square miles (59,712 acres), from the Wenatchee National Forest uplands 

to the Wenatchee River at the city of Cashmere. Figure 1 presents a map of the watershed. 

Figure 1: Map of the Mission Creek Watershed including Yaksum Creek and 

Brender Creek 

Page 4 Mission Creek Watershed DDT TMDL 

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Brender Creek, Yaksum Creek, and No Name Creek are tributaries to Mission Creek. The 

climate is characterized by mild to severe winters with hot, dry summers. Streams in the 

watershed have high flows following snowmelt in the spring and early summer. Flows naturally 

decline to minimums during the late summer and fall. During the summer critical season, stream 

flows dry up downstream from some irrigation diversions used during the critical season. Figure 

2 presents stream flow data for Mission Creek at Cashmere from 1996 through 2004. 

Figure 2: Stream flow in Liters/Second (l/s) for Mission Creek at Cashmere. 

The Wenatchee River Watershed Action Plan (WRWAP 1998) notes that soils in the valley 

bottoms differ significantly among Mission Creek (gravelly), Yaksum Creek (loamy sand to 

sandy loam), and Brender Creek (clayey, silty, and sandy loams). The WRWAP identified 

Mission Creek as the most polluted waterbody in the watershed. 

Outside of forested lands, pear and apple orchards make up the primary land use in the watershed 

along with some alfalfa and non-commercial farms. Orchards flank Mission Creek in a narrow 

band from the urban boundary of Cashmere to near the Wenatchee National Forest boundary. 

Orchards grow in the lower portion of Yaksum Creek within the confines of the valley that are 

cultivatable. Orchards are also located in the Brender Creek canyon and are more extensive where 

the valley broadens on the west side of Cashmere. 

DDT was used in Mission Creek Watershed orchards to control coddling moths and other pests 

from the 1940s to 1970s. EPA banned DDT in 1972. DDT attaches to sediments and 

particulate matter in the aquatic environment because of its low water solubility and high affinity 

for solids, especially solids with high organic carbon content. Transport of DDT to streams and 

movement within aquatic environments is often associated with erosion of contaminated soils 

and elevated loads of suspended solids (Johnson et al., 1988; Joy and Patterson, 1997). DDT and 

its breakdown products continue to be present at relatively high concentrations in the streams of 

Mission Creek Watershed DDT TMDL Page 5 

Water Quality Improvement Report 
the lower Mission Creek Watershed. Since DDT can remain stable for decades when bound to 

soils (Harris et al., 2000), it is likely that orchard soils are the major source. 

Applicable water quality criteria 

The state of Washington’s water quality standards for surface waters of the state are set in 

Chapter 173-201A of the Washington Administrative Code (WAC). 

Chapter 173-201A-240 WAC includes a provision that “Toxic substances shall not be introduced 

above natural background levels in waters of the state which have the potential either singularly 

or cumulatively to adversely affect characteristic water uses, cause acute or chronic toxicity to 

the most sensitive biota dependent upon those waters or adversely affect public health as 

determined by the department.” Numeric criteria to protect aquatic life from DDT exposure are 

set to protect the most sensitive aquatic species (EPA, 1980). The chronic criterion for DDT is 1 

nanongram per liter (ng/l) – a concentration not to be exceeded as a 24-hour average (Table 1). 

One ng/l equals one part per trillion (ppt). The acute criterion – not to be exceeded at any time – 

is three orders of magnitude higher at 1,100 ng/l. 

Table 1: Water quality criteria to protect aquatic life and human health from DDT and its 

breakdown products. 

Parameter 

Aquatic Life – 

Chronica 

(ng/l) 

Aquatic Life – 

Acuteb 

(ng/l) 

Human Health – 

Fish Tissue 

(ng/g)c

Human Healthd – 

Water and 

Organisms (ng/l) 

4,4’-DDE 1 1,100 32 0.59 

4,4’-DDD 1 1,100 45 0.83 

4,4’-DDT 1 1,100 32 0.59 

t-DDT 1 1,100 ne ne 

 aNot to be exceeded as a 24-hour average bNot to be exceeded at any time 

 c

ng/g = nanograms per gram, equal to parts per trillion in fish tissue dFor consumption of organisms and water 

 ne = not established

Human health criteria 

Criteria for the protection of human health are applied to the state through a federal rule [40 CFR 

131.36(14)]. In fresh waters, human health criteria take into account the combined exposure of 

both drinking the water and eating fish that lived in the water. In marine waters, human health 

criteria only consider the effect of eating fish that lived in the water. The state established 

criteria to protect against non-carcinogenic illness and to keep the risk of developing cancer to a 

pre-specified level. In Washington, the cancer risk is set such that no more than 1 in 1,000,0000 

people with full exposure would be likely to develop cancer in response to that exposure. Full 

exposure is defined by set assumptions on body size, fish, and water consumption, and the 

number of years exposed. For example, in Washington the risk is correlated to an average-sized 

man consuming 6.5 grams per day of fish (approximately 5 pounds per year), drinking 2 liters of 

water (if a fresh waterbody), and continuing this pattern for 70 years. People with higher or 

lower exposure patterns would face higher or lower risks. This basic exposure pattern is the 

same for both cancer-causing and non-cancer-causing chemicals. 

Page 6 Mission Creek Watershed DDT TMDL 

Water Quality Improvement Report 
In 1992, the EPA published the National Toxics Rule (NTR, 40 CFR 131.36) which set numeric, 

chemical-specific water quality criteria for priority pollutants in order to bring states into 

compliance with the Clean Water Act. 

Acceptable fish tissue concentrations are 32 nanograms per gram (ng/g) for DDE and DDT, and 

45 ng/g for DDD. One ng/g is equal to one part per billion (ppb). The NTR uses a 

bioconcentration factor of 53,600 (EPA, 1980) to translate the acceptable tissue concentrations 

into criteria for water (the tissue concentration times the bioconcentration factor equals the water 

quality criterion) – 0.59 ng/l for DDE and DDT, and 0.83 ng/l for DDD. 

Water quality and resource impairments 

Table 2 shows the 303(d) listings for DDT, DDD, and DDE in the Mission Creek watershed. The 

current (2002/2004) listings are for exceedances of the human health criteria of DDT compounds 

(DDE, DDT, and DDD). 

Table 2: Mission Creek watershed waterbodies on the 2004 303(d) list for DDT, 

DDE, and DDD.

Waterbody Parameter Medium Listing ID 

Township 

Range 

Section 

Mission Creek 4,4’-DDD Water 34832 23N 19E 04 

Mission Creek 4,4’-DDE Water 34826 23N 14E 04 

Mission Creek 4,4’-DDE Fish Tissue 8960 23N 19E 04 

Mission Creek 4,4’-DDT Water 34829 23N 19E 04 

Mission Creek 4,4’-DDT Water 8958 23N 19E 04 

Mission Creek 4,4’-DDT Fish Tissue 8959 23N 19E 04 

Brender Creek 4,4’-DDD Water 34833 23N 19E 05 

Brender Creek 4,4’-DDE Water 34827 23N 19E 05 

Brender Creek 4,4’-DDT Water 34830 23N 19E 05 

Yaksum Creek 4,4’-DDD Water 34834 23N 19E 09 

Yaksum Creek 4,4’-DDE Water 34828 23N 19E 09 

Yaksum Creek 4,4’-DDT Water 34831 23N 19E 09 

The technical report (Appendix A) presents data on DDE, DDD, and DDT as individual 

contaminants. Each of these contaminants exhibits similar chemical and toxic properties. 

Implementation actions to address each individual contaminant will be the same. For this reason, 

implementation of this TMDL addresses the contaminants as t-DDT. 

Seasonal variation 

This TMDL report considers seasonal variation by using calculated loads from pooled 

2000-2003 flow data collected over three seasons. Current loads calculated from these data are 

Mission Creek Watershed DDT TMDL Page 7 

Water Quality Improvement Report 
considered representative of seasonally-adjusted average flow conditions since they were 

collected under flow regimes ± 25 percent of average. 

Stormwater 

Currently, no municipalities are permitted to discharge stormwater by the Phase I or Phase II 

municipal stormwater permit. Stormwater from urban and rural areas in the project area is 

considered a nonpermitted, nonpoint source of potential pollution. Activities covered by the 

state’s construction or industrial stormwater permits should comply with practices identified in 

the Eastern Washington stormwater manual (Ecology, 2004). 

Data were not collected during rainfall events. Stormwater events may cause episodic loading of 

t-DDT. By setting daily TMDL targets to meet human health criteria for chronic exposure on a 

daily basis, it is assumed that the acute criteria will also be met. Water column concentrations 

measured during the present and previous studies were one to three orders of magnitude less than 

the acute water quality criterion. Ecology recommends that the implementation plan should 

include a characterization of t-DDT in stormwater discharge into surface water. 

Page 8 Mission Creek Watershed DDT TMDL 

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Technical Analysis 

Study design 

Ecology collected samples in April through June 2003. The Quality Assurance Project Plan for 

this project (Serdar and Era-Miller, 2003) describes the sampling and analysis plan designed to 

meet the project objectives. The following various types of samples were collected to assess 

transport of t-DDT to streams and to assess movement of t-DDT in the streams. 

• Upland soils were analyzed to assess whether t-DDT is sequestered at significant 

concentrations in representative orchard lands and public areas such as schools and city 

parks. 

• Bed sediments were collected from depositional areas to assess the degree to which 

sediments act as an aquatic sink for t-DDT. 

• Suspended particulate matter (SPM) was analyzed for t-DDT to assess the proportion of 

water column concentrations and loads contained in the solid phase. 

• Filtered and unfiltered water column samples were collected from the creeks to assess the 

influence of the solid and dissolved component. 

• Shallow groundwater was sampled to assess it as a potential t-DDT transport mechanism. 

Although the study design included plans to collect stormwater runoff to assess transport of 

upland soils to streams, these samples were never obtained due to logistical problems and a drier 

than normal spring (precipitation was 30 percent below normal during the 3-month study period). 

Sample locations 

Ecology selected stream sample locations (Figure 3) based on the type of data desired. Project 

field staff collected water samples and SPM at stream mouths to assess the total loading and at 

groundwater sampling locations to assess similarity between surface water and groundwater. 

Staff also collected groundwater samples based on availability of groundwater in piezometers. 

Staff collected bed sediments where fine depositional material was available. Accessibility was 

a factor in selecting all sampling locations. 

Field staff collected upland soil samples from five orchards each in the Mission Creek watershed 

and Yaksum Creek watershed, and from three orchards in the Brender Creek watershed. To 

decide which orchards to sample, staff gathered lists of addresses on road segments running 

alongside orchards. A list of parcel owners provided by the Chelan County Assessor’s Office 

was then cross-matched against these addresses. Parcel owners were telephoned in a sequence 

designed to avoid collecting samples on consecutive parcels. Landowners were informed of the 

study and asked for permission to sample. If permission was granted, staff asked landowners 

about the history of the parcels. Parcels that did not have orchards between the early 1950s and 

mid-1960s were eliminated from consideration as were parcels that had undergone major soil 

disturbance or conversion to other land uses. Locations are not shown in order to preserve the 

anonymity of private land owners. 

Mission Creek Watershed DDT TMDL Page 9 

Water Quality Improvement Report 
Upland soils were also collected from five public spaces: three ball fields, and two small city 

parks (Figure 4). Sites were selected following consultation with the Cashmere School District 

and the City of Cashmere to ensure soils were native or had been relatively undisturbed in the 

previous 50 years, and that the land had not been used as orchards or for other agriculture in the 

previous 50 years. 

Figure 3: Map of the project area with sampling locations for surface water and sediment 

sample site locations 

Page 10 Mission Creek Watershed DDT TMDL 

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Figure 4: Soil sampling site locations for the technical report. 

Data analysis 

Statistical analysis was conducted using SYSTAT® 9.01 (SPSS, Inc.). A complete discussion of 

the statistical analysis can be read in the technical report (Appendix A). 

Instantaneous loads of t-DDT were calculated using the following equation. 

instantaneous load (mg/day) = ICw x (10-6 mg/ng) x IQ (86,400 s/day) 

Where: 

• ICw = instantaneous concentration of t-DDT in unfiltered water (ng/l) 

• IQ = instantaneous discharge in l/s. 

• mg/day = milligrams per day 

• mg/ng = milligrams per nanograms 

• s/day = seconds per day 

Mission Creek Watershed DDT TMDL Page 11 

Water Quality Improvement Report 
Results 

Appendix A presents a complete analsis and the results for all parameters investigated as part of 

this project. 

DDT concentrations in surface water and shallow ground 

water 

Most of the conventional water quality parameters measured during the study appeared to fall 

into the range of usual values for the streams assessed compared to previous studies. Total 

organic carbon (TOC) concentrations were similar to those previously reported by Serdar and 

Era-Miller (2002). Based on differences between paired unfiltered water and filtered samples, 

most of the TOC is dissolved at each location. 

Flows in Mission Creek were typical for the seasons; however, Brender and Yaksum creeks had 

flows substantially below normal (WRWSC, 1998; Serdar and Era-Miller, 2002). The April 10, 

2003, Yaksum Creek discharge measurement may underestimate actual conditions but very low 

water levels made it difficult to obtain accurate measurements. 

DDT concentrations in unfiltered and filtered surface water ranged from 0.1 to 130 ng/l t-DDT, 

except at Mission Creek above the Wenatchee National Forest boundary (sample location 11MC, 

Figure 3), where no DDT was detected (Table 4). 

• The highest DDT concentrations in surface water were from the lower Yaksum Creek 

sites (7AMC and 7MC). t-DDT in unfiltered water across sites were composed of 54 

percent 4,4’-DDE, 30 percent 4,4’-DDT, and 16 percent 4,4’-DDD on average. 

In Yaksum Creek, t-DDT concentrations increased markedly – up to an order of magnitude – 

downstream of sample locationYAKPZ1. Results also suggest that Yaksum Creek entrains 

substantial particle-bound DDT in the relatively short reach between 7AMC and 7MC, although 

there are no paired samples to support this. 

t-DDT concentrations in Mission Creek show an increase between MISSPZ1 and 2MC (Figure 

3). The confluence of Yaksum Creek and Mission Creek, which is located between MISSPZ1 

and 2MC, probably accounts for the increased t-DDT concentrations between these sites. 

Brender Creek t-DDT concentrations were intermediate with respect to Yaksum and Mission 

creeks. Unlike the other streams, however, t-DDT concentrations in Brender Creek decreased 

between the upstream (BRENPZ1) and downstream (3MC) stations. The Peshastin irrigation 

spill sampled upstream of BRENPZ1 had a t-DDT concentration an order of magnitude lower 

than unfiltered water at BRENPZ1. 

The BRENPZ1 t-DDT composition was similar to other sites, but unfiltered water from 3MC 

had an unusual “fingerprint” composed of much higher 4,4’-DDD concentrations compared to 

other sites (31 percent versus 14 percent). Aside from one sediment sample in Yaksum Creek, 

the only other samples collected for this study with the “high 4,4’-DDD fingerprint” were bottom 

sediments and SPM from 3MC. 

Page 12 Mission Creek Watershed DDT TMDL 

Water Quality Improvement Report 
Approximately 20 to 80 percent of t-DDT was in the dissolved form, based on results of paired 

unfiltered water and filtered water samples. Mission Creek (2MC) paired samples indicate that 

25 percent of the t-DDT was in the dissolved phase, which agrees well with the calculated 

dissolved fraction from the SPM sample (28 percent). In Brender Creek, however, dissolved tDDT fractions calculated from paired sample analysis was in poor agreement with SPM (73 

percent and 0 percent, respectively). The high dissolved fraction was probably due to poor total 

suspended solids (TSS) removal efficiency by the centrifuge used for Brender Creek. 

No DDT was detected in groundwater samples collected from the Mission and Yaksum Creek 

sub-basins, suggesting that DDT is not traveling through groundwater in either gaining 

(Yaksum) or losing (Mission) reaches. However, the groundwater sampling for this project was 

limited and may not represent all potential groundwater pathways in the lower Mission Creek 

basin. Information obtained after sampling shows that there is a large groundwater input to 

Brender Creek in reach river mile (RM) 1.1-1.5. Absent any significant DDT load from 

groundwater, this input could account for the dilution in DDT concentrations between BRENPZ1 

and 3MC. This reach was not sampled during the present study but should be considered for 

sampling in any subsequent surveys of DDT in groundwater. 

Table 3 shows conventional parameters in surface water and shallow groundwater. DDT results 

are presented in Table 4. 

Table 3: Conventional parameters in surface water and shallow ground water. 

Location 

Sample 

Type Date 

Discharge 

(l/s) 

TSS 

(mg/l) 

SS 

(ml/l/hr) 

TDS 

(mg/l) 

TOC 

(mg/l) 

Mission Creek 

2MC Unfiltered 

water 

4/9-10/03 1,048 18 

0.4 U 

n/a 

2.4 

“ “ 5/29/03 920 19 0.4 U n/a 1.4 

“ “ 6/24/03 328 4 0.1 UJ n/a 1.4 

2MC Filtered water 4/9-10/03 1,048 n/a n/a 148 2.4 

“ “ 6/24/03 328 1 U n/a 138 2.4 

MISSPZ1 Unfiltered 

water 

5/29/03 n/a 11 

0.4 U 

n/a 

1.5 

“ “ 6/24/03 n/a 3 0.1 UJ n/a 1.3 

MISSPZ1 Ground water 5/29/03 n/a 3 n/a 240 J 1.1 

“ “ 6/24/03 n/a 1 n/a 225 1.5 

Mission Creek Watershed DDT TMDL Page 13 

Water Quality Improvement Report 
Table 3: (cont) Conventional parameters in surface water and shallow ground water.

Location 

Sample 

Type Date 

Discharge 

(l/s) 

TSS 

(mg/l) 

SS 

(ml/l/hr) 

TDS 

(mg/l) 

TOC 

(mg/l) 

11MC Unfiltered 

water 

5/28/03 681 7 

0.4 U 

n/a 

1.1 

“ “ 6/24/03 246 2 0.1 UJ n/a 1.1 

Brender Creek 

3MC Unfiltered 

water 

4/9-10/03 67 16 

0.4 U 

n/a 

2.6 

“ “ 5/29/03 68 18 0.4 U n/a 1.8 

“ “ 6/24/03 131 4 0.1 UJ n/a 1.5 

3MC Filtered water 4/9-10/03 67 n/a n/a 312 2.3 

“ “ 6/24/03 131 1 U n/a 195 2.6 

BRENPZ1 Unfiltered 

water 

5/29/03 n/a 36 

0.4 U 

n/a 

2.2 

“ “ 6/24/03 n/a 22 0.1 J n/a 1.8 

Peshastin Canal 

PESHAST1 Unfiltered 

water 

6/25/03 n/a n/a n/a n/a n/a 

Yaksum Creek 

7AMC Unfiltered 

water 

4/10/03 0.2 1 U

0.4 U 

n/a 

2.5 

“ “ “ (rep) 0.2 1 0.4 U n/a 2.6 

“ “ 6/24/03 16 14 0.1 UJ n/a 1.8 

“ “ “ (rep) 16 15 0.1 J n/a 1.6 

7AMC Filtered water 4/10/03 0.2 n/a n/a 360 2.3 

“ 6/24/03 16 1 n/a 82 3.3 

7MC Unfiltered 

water 

5/28/03 16 47 

0.4 U 

n/a 

2.4 

“ “ “ (rep) 16 45 0.4 U n/a 2.2 

Location 

Sample 

Type Date 

Discharge 

(l/s) 

TSS 

(mg/l) 

SS 

(ml/l/hr) 

TDS 

(mg/l) 

TOC 

(mg/l) 

YAKPZ1 Unfiltered 

water 

5/29/03 n/a 4 

0.4 U 

n/a 

2.0 

“ “ 6/24/03 n/a 2 0.1 UJ n/a 1.6 

YAKPZ1 Ground water 5/29/03 n/a 8 n/a 308 J 1.5 

“ “ 6/24/03 n/a 3 n/a 311 1.5 

Notes: 

Detected values in bold 

l/s = liters per second 

J = estimated concentration 

U = undetected at concentration shown 

UJ = undetected at estimated concentration shown 

n/a = not analyzed 

Page 14 Mission Creek Watershed DDT TMDL 

Water Quality Improvement Report 
Table 4: Concentrations of DDT (ng/l) in surface water and shallow ground water. 

Location Sample 

Type 

Date 4,4’-

DDE 

4,4’-

DDD 

4,4’-

DDT 

tDDT 

Mission Creek 

2MC Unfiltered water 4/9-10/03 0.3 J 0.3 U 0.1 J 0.4 

“ “ 5/29/03 1.3 0.2 J 0.9 2.4 

“ “ 6/24/03 1.6 0.5 1.1 J 3.2 

2MC Filtered water 4/9-10/03 0.1 J 0.3 U 0.5 U 0.1 

“ “ 6/24/03 0.3 J 0.3 UJ 0.3 NJ 0.6 

MISSPZ1 Unfiltered water 5/29/03 0.3 J 0.3 U 0.1 JB 0.4 

“ “ 6/24/03 0.4 0.3 U 0.2 J 0.5 

MISSPZ1 Ground water 5/29/03 0.3 U 0.3 U 0.5 U n/c 

“ “ 6/24/03 0.3 U 0.3 U 0.5 U n/c 

11MC Unfiltered water 5/28/03 0.3 U 0.3 U 0.5 U n/c 

“ “ 6/24/03 0.3 UJ 0.3 UJ 0.4 UJ n/c 

Brender Creek 

3MC Unfiltered water 4/9-10/03 2.3 1.0 0.3 J 3.6 

“ “ 5/29/03 3.6 2.1 1.3 7.0 

“ “ 6/24/03 3.1 2.1 0.8 J 6.0 

3MC Filtered water 4/9-10/03 1.6 0.8 0.2 J 2.6 

“ “ 6/24/03 1.8 1.2 0.5 J 3.5 

BRENPZ1 Unfiltered water 5/29/03 17 4.4 10 31 

“ “ 6/24/03 11 3.5 5.1 J 20 

UPBREN Unfiltered water 6/25/03 n/a n/a n/a n/a 

Peshastin Canal 

PESHAST1 Unfiltered water 6/25/03 1.8 0.4 1.0 J 3.2 

Yaksum Creek 

7AMC Unfiltered water 4/10/03 14 5.3 6.0 25 

“ “ “ (rep) 12 4.0 5.2 21 

“ “ 6/24/03 28 10 17 J 55 

“ “ “ (rep) 27 10 24 J 61 

7AMC Filtered water 4/10/03 10 3.6 4.2 J 18 

“ 6/24/03 9.1 4.1 5.1 J 18 

7MC Unfiltered water 5/28/03 62 22 49 133 

“ “ “ (rep) 59 22 47 128 

YAKPZ1 Unfiltered water 5/29/03 3.5 2.6 5.1 11 

“ “ 6/24/03 3.2 2.8 2.1 8.1 

YAKPZ1 Ground water 5/29/03 0.3 U 0.3 U 0.5 U n/c 

“ “ 6/24/03 0.3 U 0.3 U 0.5 U n/c 

Mission Creek Watershed DDT TMDL Page 15 

Water Quality Improvement Report 
Table 4 (Cont) Concentrations of DDT (ng/l) in Surface Water and Shallow Ground Water. 

Location Sample 

Type 

Date 4,4’-

DDE 

4,4’-

DDD 

4,4’-

DDT 

t-DDT 

Centrifuge Blank 4/10/03 0.5 0.1 J 0.1 J 0.7 

Field Blank 5/29/03 0.3 UJ 0.3 UJ 0.5 UJ n/c 

“ 6/25/03 n/a n/a n/a n/a 

Filter Blank 6/24/03 0.3 U 0.3 U 0.5 UJ n/c 

Notes: 

Detected values in bold

J = estimated concentration 

U = undetected at concentration shown 

UJ = undetected at estimated concentration shown 

B = concentration shown is less than five times the amount found in an associated laboratory blank 

NJ = there is evidence that the analyte is present and the concentration shown is an estimate 

n/c = not calculated 

n/a = not analyzed 

Shaded values exceed criteria

Page 16 Mission Creek Watershed DDT TMDL 

Water Quality Improvement Report 
Loading Capacity and Load Allocations 

Total DDT targets 

Ecology selected targets for t-DDT that will protect beneficial uses in the Mission Creek 

Watershed. Additionally, targets should be interpreted to apply so that water quality standards 

are met on a daily basis. As discussed in the introductory sections of this report, there are two 

sets of relevant criteria - one set to protect aquatic life through chronic exposure (1 ng/l for DDT 

metabolites or t-DDT) and another set to protect human health (0.59 ng/l for 4,4’-DDE and 4,4’-

DDT, and 0.83 ng/l for 4,4’-DDD). Both sets of criteria apply in the Mission Creek Watershed. 

A reasonable, simple, and slightly conservative approach is to use the t-DDT criterion of 1 ng/l. 

Based on the average composition of water samples (56 percent 4,4’-DDE, 17 percent 4,4’-

DDD, and 27 percent 4,4’-DDT), water with 1 ng/l t-DDT would typically meet the human 

health criteria. Conversely, selecting the human health criteria as targets could theoretically 

double the t-DDT concentration before the target was met (0.59 ng/l 4,4’-DDE + 0.83 ng/l 4,4’-

DDD + 0.59 ng/l 4,4’-DDT = 2.0 ng/l t-DDT). Both criteria must be met to comply with water 

quality standards. Meeting the 1 ng/l target for t-DDT should result in meeting the human health 

criteria for DDT, DDE, and DDD. 

The percent reduction of DDT loading necessary to meet the t-DDT criteria are called the target 

loads. Target loads are based on the loading capacity of the water body. Target loads for t-DDT 

were calculated for Mission, Brender, and Yaksum creeks (Table 5). Target loads were 

calculated using the formula: 

Target Load (mg/day) = CCw x (10-6 mg/ng) x HMQ x (86,400 s/day) 

Where: 

• CCw = DDT criterion in unfiltered water (ng/l) 

• HMQ = harmonic mean discharge (l/s 

Harmonic mean discharge for Mission Creek at Cashmere is 138 liters per second (l/s) based on 

data from May 1996 through April 2004 (no data for water years 2000 and 2001). Harmonic 

mean discharge for Brender Creek at Cashmere is 86 l/s based on data from February 1997 

through January 2004 (no data for water years 2000 and 2001). Yaksum Creek discharge has a 

harmonic mean of 18 l/s based on 15 measurements taken by the Chelan County Conservation 

District (CCCD) (1995-1996) and Ecology (2000, 2003). 

Table 5: Load reductions required to meet target t-DDT loads in Mission, Brender, and 

Yaksum Creeks. 

Stream/Location 

Harmonic 

Mean 

Discharge 

(l/s) 

t-DDT 

Criterion 

(ng/l) 

Target 

Load 

(mg/d) 

Average 

t-DDT 

(ng/l) 

Current 

Load 

(mg/d) 

Load 

Reduction 

(mg/d) 

Load 

Reduction 

(%) 

Mission Creek – 2MC 138 1 12 3.2 38 26 69 

Mission Creek – MISSPZ1 97 1 8.4 0.4 3.4 (5.0) (150) 

Brender Creek – 3MC 86 1 7.4 11 84 77 91 

Brender Creek – BRENPZ1 37 1 3.2 26 83 80 96 

Yaksum Creek – near mouth 18 1 1.6 62 96 94 98 

( ) = reserve capacity 

Mission Creek Watershed DDT TMDL Page 17 

Water Quality Improvement Report 
The percent reduction load allocation for t-DDT presented in Table 5 is calculated based on the 

harmonic mean discharge. To meet requirements of the Clean Water Act, it is assumed that the 

percent reduction for each site in the watershed will apply to the daily time scale and longer so 

that water quality standards for t-DDT will be met on a daily basis. Table 5 also shows current tDDT loads for each stream using the formula: 

Current Load (mg/day) = ACw x (10-6 mg/ng) x HMQ x (86,400 s/day) 

Where: 

• ACw = average concentration of DDT in unfiltered water (ng/l) based on pooled 2000 and 

2003 data 

• HMQ = harmonic mean (reciprocal of the arithmetic mean of the sum of the reciprocals 

of a specified set of numbers) discharge (l/s) 

Current loads are considered representative of average flow conditions since they were collected 

under flow regimes ± 25 percent of average. 

The greatest t-DDT load reductions are required in Yaksum Creek (98 percent reduction) and 

Brender Creek where >90 percent reductions are required to meet target loads. Mission Creek at 

MISSPZ1 (see Figure 3) has a reserve capacity (i.e., amount below assimilative capacity) of 5 

mg/day, whereas 2MC requires a 69 percent (26 mg/day) load reduction to meet its target load. 

Meeting the target load at 2MC should be achievable if the current t-DDT load in Yaksum Creek 

is reduced by approximately 30 percent. This should be possible even if the load at MISSPZ1 

approaches its assimilative capacity. 

In Brender Creek, current t-DDT loads at the upstream location (BRENPZ1) and at the mouth 

(3MC) are nearly equal as are the load reductions required to meet targets. The result of meeting 

the target load at BRENPZ1 could theoretically yield 3 mg/day reserve capacity at 3MC. 

Margin of safety 

This TMDL evaluation incorporates the following assumptions which provide a margin of 

safety. 

• The target numerical water quality criterion (1 ng/l) is conservative because at this 

concentration human health criteria will be met based on the typical composition of water 

samples (56 percent 4,4’-DDE, 17percent 4,4’-DDD, and 27 percent 4,4’-DDT). In the 

present study, all water samples with t-DDT < 1 ng/l met the individual criteria for 4,4’-

DDE, 4,4’-DDD, and 4,4’-DDT. Conversely, selecting the human health criteria as 

targets could theoretically double the t-DDT concentration before the target was met 

(0.59 ng/l 4,4’-DDE + 0.83 ng/l 4,4’-DDD + 0.59 ng/l 4,4’-DDT = 2.0 ng/l t-DDT). The 

target numerical water quality criterion was used to calculate target loads. 

• The use of harmonic mean discharges to calculate target loads increases the margin of 

safety since harmonic means are lower than arithmetic means, especially in cases where 

discharge data have a wide spread. For instance, the harmonic mean discharge in 

Page 18 Mission Creek Watershed DDT TMDL 

Water Quality Improvement Report 
Mission Creek (2MC) is 138 l/s whereas the arithmetic mean is 658 l/s. Target t-DDT 

loads calculated using the harmonic and arithmetic mean flows are 12 mg/d and 56 mg/d, 

respectively, with the former, more conservative target used in this assessment. 

Mission Creek Watershed DDT TMDL Page 19 

Water Quality Improvement Report 
Page 20 Mission Creek Watershed DDT TMDL 

Water Quality Improvement Report 
Summary Implementation Strategy 

Implementation overview 

The goals of this implementation plan are to: 

(1) Provide guidance for reducing and/or preventing the impacts of pollution 

sources to water bodies within the Mission Creek Watershed 

(2) Provide a strategy to meet water quality standards. 

Several milestones in the development of the TMDL are worth noting. Field studies addressing 

the 303(d) listed parameters were developed and conducted by Ecology from 2002-2004, with 

assistance from the CCCD. Technical analyses of the studies were completed from 2004-2006. 

Numerous drafts of the technical reports were reviewed and commented on by the WQTS and 

WWPU. Ecology responded to the comments and incorporated them into the technical reports. 

Scientists conducting the work provided numerous presentations and engaged in discussions with 

the group. 

The WQTS and WWPU assisted Ecology with development of this submittal document from 

2005-2007. The process included education, outreach, and assistance with media coverage. 

Implementation plan development 

This summary implementation strategy (SIS) was developed with input from several members of 

the WQTS. Implementation of many action items published in the final Wenatchee Watershed 

Management Plan (WWMP) should help lower t-DDT loading to Mission Creek, its tributaries 

and the Wenatchee River. Activities fall into one of three categories: implementation of an 

existing law or rule; implementation of educational and voluntary measures to protect water 

quality; and monitoring and reporting activities related to water quality improvements. 

Implementation activities 

The following actions were developed by the WQTS and are based on recommendations from 

the TMDL technical study, DDT Contamination and Transport in the Lower Mission Creek 

Basin, Chelan County, Total Maximum Daily Load Assessment (Serdar and Era-Miller, 2004). 

These activities are published in the WWMP. Adaptive management may identify other 

activities that would contribute to meeting the targets identified in this TMDL. 

If implemented, the nonpoint source control activities listed here should address the 303(d) 

listings for DDT, DDD, and DDE in this TMDL for Mission Creek, Brender Creek, and Yaksum 

Creek by 2018. 

Implementation Action Item #1. Significant reductions in DDT loads may be achieved by 

preventing bank erosion or by other means of limiting transport of upland soils to 

streams. Best Management Practices (BMPs), such as riparian buffers and wetlands, can 

also filter and uptake DDT from surface and groundwater (Burgoon, 2002). Many BMPs 

are currently being implemented in the watershed. BMPs should be continued, refined, 

Mission Creek Watershed DDT TMDL Page 21 

Water Quality Improvement Report 
and expanded to further reduce erosion, surface runoff, TSS in the water column, and 

groundwater transport of DDT. BMPs include farm practices, storm water runoff, 

riparian vegetation planting, orchard conversions, residential practices, riparian buffers, 

wetlands, etc. These and other appropriate BMP actions BMP and locations should be 

coordinated by members of the Planning Unit and its committees. 

Implementation Action Item #7. Activities should be identified and undertaken to provide 

ongoing outreach, education, and technical assistance to growers, streamside landowners, 

developers, and the general public. 

Implementation Action Item #9. Development over old orchards is a potential concern. 

Measures should be implemented to prevent DDT-laden orchard soils, disturbed during 

construction, from being transmitted to streams and lakes in the watershed. Language 

requiring measures to prevent DDT-laden soils from entering the waterways during and 

after construction should be developed by and included in county and municipality 

development ordinances, growth management plans, and critical area ordinances. The 

Stormwater Management Manual for Eastern Washington or an equivalent document 

should be utilized in developing ordinances, and guiding municipal, private, and 

construction stormwater practices. 

Specific BMPs should be coordinated between individual land owners/land managers and agency 

staff with proper qualifications to plan BMPs. For example, the CCCD, U.S. Department of 

Agriculture (USDA) and Natural Resource Conservation Service (NRCS) employ staff members 

that are trained to design conservation plans for farms. 

In addition to these implementation actions from the Wenatchee River Watershed Management 

Plan (WRWMP), the Washington State Department of Agriculture (WSDA) Waste Pesticide 

Program provides a means to reduce the potential for release of DDT contamination to the 

environment. Annually, the Waste Pesticide Program provides the opportunity for farmers in the 

Wenatchee River Watershed to turn in old and unusable pesticides to the WSDA for proper 

disposal. The collection of concentrate product greatly reduces the potential for additional DDT 

release to the environment and loading to streams in the Mission Creek Watershed. 

Implementation activities table 

The table below contains general suggestions for voluntary and required actions to be made by each 

of the entities involved with the implementation of the Mission Creek Watershed DDT TMDL. 

Implementation actions will be described in more detail in the WQIP. Some actions are dependent 

upon funding and cooperative agreements. Some actions are voluntary and others are regulatory. 

Actions may be subject to change based on the feedback and responses from potential contributors, 

ongoing adaptive management, and regulatory requirements. 

Page 22 Mission Creek Watershed DDT TMDL 

Water Quality Improvement Report 
Table 6: Organization of TMDL entities and their contributions. (A list of acronyms is 

provided at the end of the table). 

YEAR 

Implementation Action 

Item Potential Cooperators 

2008 2008-16 2012 2013 2017 2018 2020 2021 

Complete WQIP 

X 

BMPs to reduce DDT 

transport to surface 

waters (#1) 

WQTS, WWPU, CCCD, Ecology, Agriculture, 

CC, developers, municipalities, other 

stakeholders 

X 

Monitor BMPs and DDT 

targets (#2) 

WQTS, WWPU, CCCD, Ecology, Agriculture, 

CC, developers, municipalities, other 

stakeholders 

X X 

Monitor during rain 

events, spring thaw, and 

irrigation (#3) 

WQTS, WWPU, CCCD, Ecology, other 

stakeholders 

X 

Ground water monitoring 

(#4) 

WQTS, WWPU, CCCD, Ecology, other 

stakeholders 

X 

Icicle-Peshastin 

Irrigation canal DDT 

monitoring, BMPs (#5) 

WQTS, WWPU, CCCD, Ecology, IPID, other 

stakeholders 

X 

Irrigation sediment 

transport, BMPs (#6) 

WQTS, WWPU, CCCD, Ecology, irrigation 

districts, other stakeholders 

X 

Education outreach and 

technical assistance (#7) 

WQTS, WWPU, CCCD, Ecology, Agriculture, 

CC, developers, watershed groups, 

municipalities, other stakeholders 

X 

Provide funding and 

identify monitoring 

entities (#8) 

Ecology, WWPU, agencies, other funding entities 

X 

Development 

ordinances (#9) 

CC, municipalities 

X 

Waste Pesticide 

Program 

WSDA 

X X X X X X X X 

Collect data at points of 

compliance 

Ecology, other stakeholders 

X X 

Review data and targets Ecology 

X X X 

Implement adaptive 

management changes 

Ecology 

X X X X X X 

Water Quality standards 

met 

Ecology and EPA determine 

X 

Mission Creek Watershed DDT TMDL Page 23 

Water Quality Improvement Report 
The following abbreviations are used in Table 6: 

BMP Best management practices 

CC Chelan County 

CCCD Chelan County Conservation District 

CDHD Chelan-Douglas Health District 

DDT dichloro-diphenyl-trichloroethane 

DNR Department of Natural Resources 

Ecology Washington State Department of Ecology 

EPA Environmental Protection Agency 

IPID Icicle-Peshastin Irrigation District 

WWPU Wenatchee Watershed Planning Unit 

TMDL Total Maximum Daily Load 

WQTS Water Quality Technical Subcommittee 

WSDA Washington State Department of Agriculture

Reasonable assurances 

This TMDL addresses only nonpoint sources of pollution, so formal reasonable assurance is not 

required. This TMDL was developed with intense collaboration by the Wenatchee Watershed 

Planning Unit WQTS. Many action items published in the Wenatchee Watershed Management 

Plan, if implemented, will help control t-DDT transport to surface waters in the Mission Creek 

Watershed. Monitoring and adaptive management of implementation actions will help direct 

appropriate actions to reduce t-DDT loading to surface waters of the Mission Creek Watershed. 

Adaptive management 

The Mission Creek Watershed DDT TMDL is the result of a partnership between Ecology and 

the WWPU and WQTS. Ecology published this TMDL after the WQTS reviewed and 

commented on the technical report, titled DDT Contamination and Transport in the Lower 

Mission Creek Watershed, Chelan County Total Maximum Daily Load Assessment. 

Additionally, the WQTS helped develop and review the SIS for this TMDL. 

Information presented in this TMDL represents the current state of knowledge regarding DDT in 

the Mission Creek Watershed. It is the understanding of the WQTS that additional studies may 

be performed to fill data gaps and to determine the effectiveness of implementing actions 

identified in this SIS or the WQIP. 

A WQIP will be developed for this TMDL that will include a monitoring plan to evaluate 

implementation measures. If planned implementation activities do not produce the expected or 

required results, Ecology, members of the WQTS, or other entities may choose to perform more 

studies to identify significant sources of t-DDT to the creeks in the study area. The direction of 

the TMDL may be modified as a result of future monitoring results. 

Monitoring strategy 

Monitoring is an important part of this implementation strategy. Monitoring related to this 

TMDL should track implementation actions and track water quality improvements that result 

from implementation actions. In addition, monitoring conducted related to this TMDL should 

comply with the Water Quality Data Act (WQDA) codified in RCW 90.48.570 through 

Page 24 Mission Creek Watershed DDT TMDL 

Water Quality Improvement Report 
90.48.590 and Ecology’s Water Quality Program Policy 1-11. Ecology is responsible for 

effectiveness monitoring programs that determine if TMDL targets are being met. There are 

many types of monitoring that local government and organizations could effectively conduct. 

Listed below are action items from the WWMP describing monitoring needs related to this 

TMDL. These action items are presented as they are written in the WWMP. 

Implementation Action Item #6. Assessments are recommended for all irrigation systems 

in the watershed to identify any mechanisms that may contribute to sediment transport 

which are not yet being addressed by BMPs. Actions should be identified and 

implemented to address the findings. 

Implementation Action Item #4. More comprehensive groundwater monitoring should be 

conducted, including further assessment of the relationship between surface water, 

groundwater, and the fate and transport of DDT compounds. 

Implementation Action Item #2. A phased monitoring approach should be conducted to 

assess the effectiveness of BMPs and DDT-TSS reduction efforts. This may take time to 

achieve as TSS loads are reduced and DDT levels are monitored. 

Implementation Action Item #3. Evaluation of soil transport to streams should be 

conducted during large rainfall events when visual observations can be made and/or 

sections of streams with high sediment runoff and TSS can be isolated. An assessment 

should be conducted to investigate if any other events contribute soil to streams such as 

spring thaw processes or irrigation practices. 

Implementation Action Item #10. Assessments are recommended for stormwater control 

systems in the watershed to identify any mechanisms that may contribute to sediment 

transport which are not yet being addressed by BMPs. Actions should be identified and 

implemented to address the findings through a list of prioritized projects. 

Implementation Action Item #5. An assessment should be conducted to investigate if the 

Icicle and Peshastin canals are transporting DDT. It is not certain how canals may 

transport DDT since no wastewater enters the systems and most canals are lined. Current 

irrigation system BMPs should continue that maintain lined canals and limit rapid 

increased flows during non-emergency situations. Lining of any remaining unlined 

canals should be encouraged. Other BMPs include actions such as irrigation water 

management, irrigation return drain monitoring and efficiencies, irrigation spill points 

where erosion control can be reduced, spoil pile placement, and maintaining canyon 

crossings. 

Ecology will complete an effectiveness monitoring plan and present it in the WQIP, which is due 

one year after EPA’s approval of this TMDL. 

Mission Creek Watershed DDT TMDL Page 25 

Water Quality Improvement Report 
Potential Funding Sources 

The Wenatchee Watershed Management Plan identified Ecology’s grants program as a potential 

funding source for implementation activities. A variety of funding sources could be pursued by 

various members of the WQTS or other stakeholders. Listed below is an action item from the 

WWMP that describes the WWPU’s plans for seeking funding sources. A more thorough 

presentation of funding sources will be presented in the WQIP. 

Implementation Action Item #8. The Department of Ecology may provide funding 

assistance through its grants and loans programs to implement actions and ongoing 

monitoring. Other funding sources should be identified and applications submitted to 

provide funding for ongoing activities. 

Page 26 Mission Creek Watershed DDT TMDL 

Water Quality Improvement Report 
References Cited 

Burgoon, P. and P. Cross. (2002-2004) Manson Lakes Water Quality Assessment: Lake Trophic 

Status and DDT and Phosphorus Load Evaluation. Lake Chelan Reclamation District. 

Grant No. 0200114, administered by the Washington State Department of Ecology, 

Olympia, WA. 

EPA (1980) Ambient Water Quality Criteria for DDT U.S. Environmental Protection Agency. 

Office of Water Regulations and Standards, Criteria and Standards Division. 

Washington, D.C. EPA 440/5-80-038. 

EPA (2001) Overview of Current Total Maximum Daily Load – Program and Regulations. 

U.S. Environmental Protection Agency. www/epa/gov/owow/tmdl/overviewfs/html

Harris, M.J., L.K. Wilson, J.E. Elliott, C.A. Bishop, A.D. Tomlin, and K.V. Henning. (2000) 

Transfer of DDT and Metabolites from Fruit Orchard Soils to American Robins (Turdus 

migratorius) Twenty Years after Agricultural Use of DDT in Canada. Archives of 

Environmental Contamination and Toxicology. Vol. 39, pp. 205-220. 

Johnson, A., D. Norton, and B. Yake. (1988) Persistence of DDT in the Yakima River 

Drainage, Washington. Archives of Environmental Contamination and Toxicology. Vol. 

17, pp. 289-297. Washington State Department of Ecology, Olympia, WA. Publication 

No. 88-e17. 

Joy, J. and B. Patterson. (1997) A Suspended Sediment and DDT Total Maximum Daily Load 

Evaluation Report for the Yakima River. Washington State Department of Ecology, 

Olympia, WA. Publication No. 97-321. 

Serdar, D. and B. Era-Miller. (2002) Pesticide Monitoring in the Mission creek Basin, Chelan 

County. Washington State Department of Ecology, Olympia, WA. Publication No. 02-

03-022. 

Serdar, D. and B. Era-Miller. (2003) Quality Assurance Project Plan – Total Maximum Daily 

Load Study: DDT Contamination and Transport in the Lower Mission Creek Basin, 

Chelan County, Washington. Washington State Department of Ecology, Olympia, WA. 

Publication No. 03-03-103. 

Serdar, D. and B. Era-Miller. (2004) DDT Contamination and Transport in the Lower Mission 

Creek Basin, Chelan County: Total Maximum Daily Load Assessment. Washington State 

Department of Ecology, Olympia, WA. Publication No. 04-03-043. 

WRWSC. 1998. Wenatchee River Watershed Action Plan. Wenatchee River Watershed 

 Steering Committee. Wenatchee WA 

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Appendix A 

This TMDL’s technical report DDT Contamination and Transport in the Lower Mission Creek 

Basin, Chelan County can be viewed at the following web site: 

http://www.ecy.wa.gov/biblio/0403043.html 

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Appendix B 

Responsiveness Summary to Comments Received During Public Comment Period. 

Ecology held a public comment period for this report from May 23, 2007 to June 22, 2007. The 

public comment period was advertised in the following Chelan County newspapers: 

• The Leavenworth Echo 

• The Cashmere Valley Record 

• The Wenatchee World 

Ecology received the following comment during the public comment period: 

Re: the most impassioned plea I made many months age regarding clarity and 

understandability in the DDT report. 

Could you state at least once in the report what an ng/l or an ng/g means? 

It might be interesting to the public, and informative if we said "parts per 

trillion" or something that the mind can grasp as being very, very small. An 

ng/L means nothing. 

The public is not being informed, just alarmed, by ng/l. 

Ecology’s response to the comment: 

Response: Ecology incorporated your suggestion to the report. The first time we use nanograms 

per liter (ng/L) in the report and the report’s executive summary, we also state that 1 ng/L is 

equal to one part per trillion. In addition we added that a nanogram per gram is equal to one part 

per billion in the portion of the report that ng/g is used. 

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