Dog Kennel Septic System

**Park Headquarters, Puerto Ayora, Santa Cruz Island**

On Monday June 5, 2000 I met with Jeff, the hunt dog coordinator and we
went to the new dog kennel facility which is just being completed. The
project presented for my review is the design and configuration of the
wastewater systems for the facility which are required for hunt
operations, but are desired by the park to be designed to prevent
contamination of the sub surface water supply.

The present configuration of the kennel has a capacity of fifty dogs in
the facility, which is split into two areas, which for this report I
will refer to as the north septic (NS) and the south septic (SS)
systems. Currently the plumbing discharge lines and junction boxes have
been installed, and work has begun to excavate for the two septic tanks.
The SS is also required to service the office/food preparation facility.
It is also proposed that the kennel facilities may be expanded in the
future and an additional septic system may be required.

On Tuesday June 6, I met with Carlos, the Park Engineer and we discussed
the design for the septic tanks, possible solutions to include
evapo-transpiration (ET) of septic effluent and inspected the current
site conditions. I told him to proceed with the tank construction and
found there are adjacent areas, which may function for the ET site. Site
conditions are very difficult for excavation in the dense lava materials
and blasting may be required to install the septic tanks. The areas for
the ET beds are also constrained by terrain and grade for gravity flow
from the septic tanks. The septic tanks will be constructed to the
current design for the islands, with a three stage tank, with the third
chamber being an open bottom chamber semi filled with rock as a filter
to the grotto below, with very limited contact time for treatment. We
had discussion on leach systems, the infiltrator chambers,
evapo-transportation and local material design.

With a 50 meter transect tape I measured the ET bed sites for the dog
kennels. The NS bed is located 18.5 meters to the west of the septic
tank and will provide a bed size of 6x9 meters (54 m².). The SS is more
restricted by terrain and is located to the south adjacent (3.5 meters)
to the septic tank and will provide a bed size of 6x8 meters (48 m².)

Recommendations-

Short Term- Proceed with the construction of the septic tanks of the
standard island design with four important design modifications.

1.  Provide a top access opening (Boca de vista) into the third filter
    chamber to allow for making the plumbing connections to connect to
    the evapo-transpiration beds. The discharge line to the bed will be
    installed through an opening drilled through the side of the
    chamber.

2.  Seal the inside of the first and second chambers of the septic tanks
    to prevent groundwater intrusion or leakage of untreated liquids
    into the groundwater aquifer.

3.  Install piping "Tee" baffles on the first chamber inlet and outlets
    of both chambers to prevent transfer of surface scum and untreated
    materials. Between the chambers only one 4" pipe is required. The
    boca de vistas should be positioned to allow for inspection and
    cleaning of the inlet of the camara de acumulacion, the outlet of
    the camara de sedimentacion, and a small boca provided above the
    first chamber discharge to allow for maintenance. See the diagram
    next page-

4.  The discharge from the floor and sink in the kitchen should join in
    a junction box which will function as a grease trap, and than be
    plumbed to enter the camara de acumulacion of the septic tank. It
    will be very important to stress to the workers preparing the dog
    food to avoid flushing any grease, animal fat or bone into the waste
    water system to avoid clogging the lines. The grease trap box will
    require regular cleaning to remove any accumulated materials.

Water conservation both as a supply and as a wastewater treatment
concern should be an important consideration in the operation of this
facility. The idea of using fresh water to wash dog waste into a drain
for treatment may require a second thought. Water should be used to keep
the kennels clean and sanitary, but accumulations of fecal matter should
be manually collected and disposed of. Three options exist for the
disposal. 1. Haul to the municipal dump, which is less preferred due to
sanitation concerns, waste of important man-hours and resources. However
regular dump trips will be required to dispose of animal byproducts from
the butchering operation so some dog waste can also be disposed of in
this manner. 2. Construct a sealed dry compost pit for solid waste
decomposition. This option is least desired, as some biological leaching
into the sub surface area will occur. 3. Dispose of dog fecal matter
directly into the camara de acumulacion of the north system septic tank.
This is the recommended preferred option as the north system is lightly
loaded and has the capacity for the installation of the larger ET
system. However care should be taken in this process to only dump fecal
matter while avoiding bones, other trash items and sand/rock matter,
which will eventually fill the camara de acumulacion.

Long Term- Construct Evapo-transpiration beds to perform final treatment
of the septic effluent and discharge of liquids into the atmosphere.
This will allow for sanitary waste treatment and prevent effluent
discharge into the sub surface aquifer, which provides water to the park
facilities. Attached to this report are design criteria for the sizing
of the ET beds and construction specifications.

If the kennel facilities are expanded an additional septic system is
required it is recommended that tank location and ET bed site location
be given important consideration. The low area in the center of the
kennel compound may be desirable as the new kennel sewage lines could
flow to the central point and the low area can provide the ET bed site
with minimal surface disturbance. A more cost-effective alternative may
be to install a pump and utilize the existing North Septic system that
has the capacity to handle the additional 300 liters per day the new
facilities could generate.

This report is site specific for the dog kennel facility, but the
calculations on evaporation and systems sizing can readily be adapted
for other waste treatment facilities in the Puerto Ayora area.

Kent Bullard

Maintenance Supervisor

Channel Islands National Park

<kent_bullard@nps.gov>

**On-Site Disposal of Waste Water through Evapo-Transpiration**

**System Calculation and Design Criteria**

**Isla Santa Cruz, Galápagos, Ecuador**

**1. INTRODUCTION**

Domestic wastewater disposal in the islands has traditionally involved a
three-stage septic tank in which the last chamber is rock filled, open
on the bottom and acts as a filter for the final effluent. This system
in conjunction with existing sub terrain features of extremely porous
lava material does not allow for sufficient contact and treatment time
before the effluent comes into contact with the sub surface fresh water
aquifer. This has resulted in the contamination of the aquifer and
problems for the population in obtaining safe potable water. The
availability of and type of building materials obtainable on the island
limit options in the design and construction of on site effluent
treatment facilities.

**2. OVERVIEW OF SYSTEM COMPONENTS**

Liquid sewage wastes are treated in a sealed, locally constructed two
stage concrete septic tank of a nominal liquid capacity of 3,900 liters
(1,000 gallons). 2M x 2.45M x 1.5M exterior dimensions.

Waste liquid volumes are reduced through practice of water conservation
and it is estimated that for the North Septic System (NS) daily flow
will be less than 150 liters. The South Septic System (SS) flow will be
higher as it also serves the office with bathroom (toilet and sink), the
veterinarian office with sink, and the kitchen used to prepare food for
the dogs. The estimated flow for the SS is 450 liters per day. This will
allow for a minimum of eight days of contact time in the septic tank for
treatment.\
\
A grease trap is a simple tank, which allows any particulate matter from
the kitchen drain system to settle out. Oil, fats and other materials,
which are lighter, than water and remain on the surface, are separated
in this manner and can be manually, removed to prevent clogging of the
septic system.

An Evapo-transpiration (ET) Bed, a locally constructed sand and gravel
bed, plastic lined and planted with native grass and shrubs, recycles
the final effluent waste through evaporation and transpiration.

**3. WASTE VOLUMES**

The initial sizing of the septic tank and evapo-transpiration treatment
bed is determined by the amount of waste flow expected from each
facility.

**Toilet Flows**

It is assumed that the flow rate from the toilet system will be 3.25L
(0.9 USG) per use. As this is a daytime only work facility with limited
staff use is assumed that less than 30 flush cycles will occur daily. A
sign above the toilet, suggesting to only flush when required will help
to conserve water supplies and reduce septic system loading.\
**Other Flows**

Waste from the sinks in the toilet, veterinary office and food
preparation facility are assumed to be for primarily cleaning actions
and estimated at 200L per day.

The wash down water effluent from the kennel facilities is estimated at
150L per day, based on cleaning the 25 dog kennels.

**Total flows**

Based on these figures total flows for the North System would be 150L,
and the South System would be 450L.

For reference below is a table, which shows, assumed wastewater flown
for households practicing water conservation.

**Assumed total Wastewater Flows from Households of Different Sizes**

  ------------------- --------------------------- ------------------------
  \# Persons          Flows                       

                      Liters/Day                  US Gal./Day

  1                   165                         44

  2                   330                         87

  3                   495                         131

  4                   660                         175

  5                   825                         218

  6                   990                         262
  ------------------- --------------------------- ------------------------

**4. GREASE TRAP**

A simple grease trap is required to allow the small amounts of
particulate matter in the gray water to settle out, while at the same
time separating oil, fats and other materials, which are lighter than
water. The use of a grease trap prevents solids from clogging up and
reducing the effectiveness of the septic tank and evapo-transpiration
bed.

 

The design of a grease trap is very simple, and because it is not
handling toilet wastes, the trap need only be big enough to handle 24
hours gray water output from the kitchen sink. Based on the above flow
rates, the existing grease trap at .5m X .5m has a capacity to handle
the estimated 200 liter flow per day.

**5. EVAPO-TRANSPIRATION (ET) BED**

**5.1 How It Works**

An Evapo-Transpiration Bed works to evaporate waste liquids in three
main ways:

\- Natural Evaporation

\- Transpiration of Plants

\- Increased evaporation from the heat energy of bacterial action

Precipitation penetrating the bed must then be subtracted from the total
impact of these three factors to find the net evaporation performance of
an ET Bed.

Once these factors are known (as the are from monthly weather records at
Puerto Ayora) it is a relatively simple matter to determine the size of
the bed required to handle the amount of waste water being produced.

The method of calculating natural evaporation figures, and the numbers
for Puerto Ayora (for 1995, considered an average weather year), are
shown at Appendix 1, while the figures for transpiration and bacterial
action are shown at Appendix 2 and 3 respectively. Precipitation numbers
are shown at Appendix 4.

As shown below the results from adding these factors together for Puerto
Ayora, varies from a low figure for net evaporation/transpiration of
4.3mm. (0.34\") per day in December to 11.8mm. (0.46\") per day in
April.

  [Table 2]{.underline}

**Net Daily Evaporation By Month, 1995, for Puerto Ayora, Isla Santa
Cruz**

 

  ----------------- ----- ------ ------ ------ ------ ------ ------ ------ ------ ----- ----- -----
                    Jan   Feb    Mar    Apr    May    Jun    Jul    Aug    Sep    Oct   Nov   Dec

  mm\. per Day      4.4   10.5   11.2   11.8   11.4   10.6   10.7   10.5   10.1   8.8   8.2   4.3

  Inches per day    .18   .4     .45    .46    .44    .41    .43    .42    .41    .37   .37   .34

  Liters/day /M²    4.4   10.5   11.2   11.8   11.4   10.6   10.7   10.5   10.1   8.8   8.2   4.3
  ----------------- ----- ------ ------ ------ ------ ------ ------ ------ ------ ----- ----- -----

**5.2 Building an Evapo-transpiration (ET) Bed**

 

ET Beds are simple and very inexpensive to construct. Bed calculations
shown in this guide are based on a bed depth of 60cm. Because the
calculated level of liquid in the bed is never closer than 30cm from the
surface, the 60cm depth provides a safety reservoir.

The bed should be located so that the output from the septic tank will
flow naturally into the ET bed with a gentle slope at the interface
between the gravel and sand layers.

As the ET bed is to be built over rocky ground, a sand or fine crushed
lava layer about 2.5cm deep should be placed under the plastic sheet.
This material should be compacted to prevent settlement and is important
as it protects the plastic lining the bed from puncture.

The plastic liner should be 3 layers of black or clear plastic, 10 mil.
thick and should be extended upwards around the sides so that the upper
edge of the sheet is right up to the surface level. The sheet should be
supported from the outside by a berm of fine crushed lava or sandy
material. If an overlap of the sheets is required, this should be about
50cm (20\") wide to keep the bed watertight.

Immediately above the sheet 2.5cm of sand or fine crushed lava material
should be used to protect the sheet from sharp stones, and above this
the bed should be filled with a 15cm base of loosely placed 1cm-2cm
crushed lava material. Immediately on top of the 1-2cm material, a 4\"
perforated plastic sewer pipe, placed 1 meter from the edge of the bed
and 2.5-3 meters apart, and should be placed with a gradient of 1-2^o^.
It is preferable to attach a 4\" ventilation pipe at the end of the
distribution pipe, with a hood surmounting it, to assist in providing a
greater supply of oxygen to the ET bed. Both ends of the pipes are
connected forming a circle of pipe in the bed. This is desirable to
allow flow around the bed system in case one lateral line was to become
clogged by debris. The 4" perforated pipes are than covered with 1-2cm
material, covering and surrounding the pipes by 5-7cm. If the perforated
pipes are not locally available, the pipes can be manufactured by
drilling a 1cm hole spaced at 10cm intervals on both sides of the pipes
on a line 1/3 of the way up from the bottom. If possible bring the
supply pipe from the septic tank over the berm. If this is not possible
to grade or site conditions the entry through the berm must be sealed to
prevent leakage around the pipe. Use mortar, plastic tape/glue or
similar sealing materials.\
\
Above the 1-2cm crushed lava material (gravel) layer, the bed should be
filled with 45cm of fine crushed lava of a grain size of about 1mm. (4
mil.). After settling, the bed should be filled so that it has a center
crown of about 15cm above the sidewalls for diversion of rain. The bed
should be level or above the surface of the surrounding terrain around
the perimeter to prevent rainwater runoff from entering the bed.

Putting no more than a sprinkle (1cm) of topsoil on the surface, a cap
is than formed which will help seal the surface and promote runoff of
rains. Native grass such as the Sedge should be plug (bare root) planted
in the bed. Additionally some native shrubs can also be planted
(bare-root) in the bed. About 25-30 Sedge should be planted per square
meter and one shrub per square meter. These plants are crucial in
performing evapo-transpiration functions. The ideal shrubs should be
each about 30-45cm high when planted. Dr. Mark Gardner of the Darwin
Station can provide further information on the types of native plant
materials to use.

**5.3 Sizing An ET Bed\
**

An ET bed may be sized in the following way:

i\) Determine the amount of wastewater per month the ET bed is to be
designed to handle.

In this system a figure of 450 Liters per day, or 13,500 Liters per
month is assumed. And the design criteria will address the South System,
which has the greatest waste flow.

 

ii\) Determine the net average daily evaporation through the whole year
in Liters/month/M² by:-

a\) Adding together the \"Net Daily Evaporation by Month\" in
Liters/day/M² for every month of the year. (See Table 2)

b\) Divide by 12 to obtain the average net monthly figure

c\) Multiply by 30 to get average monthly evaporation in Liters

per month per square meter.

 

In Puerto Ayora this average monthly figure (calculated from table 2) is
112.5/12 X 30 = 281 Liters per month per square meter of ET bed.

iii\) Divide the assumed monthly wastewater volume (in this case 13,500
Liters) by the monthly evaporation per square meter. (281 Liters) to
determine the number of square meters required .

In Puerto Ayora this works out to 13,500/281 or a bed size of 48 M² for
the South Septic System.

For a residence in Puerto Ayora of 5 people, with a monthly flow of
25,000 Liters a bed size of 88 M² would be required, or about 17.5 M² of
ET bed per person. Table 3 below shows the required bed size in Puerto
Ayora for different household sizes, assuming a total output of 165
Liters per person per day.

[Table 3]{.underline}\
Required ET Bed Size in Puerto Ayora for Differing Household Sizes

 

  ------------------------------- ---------------------------------------
  \# People                       ET Bed M²

  1                               17.5

  2                               35

  3                               52.5

  4                               70

  5                               87.5

  6                               122.5
  ------------------------------- ---------------------------------------

For interest, Appendix 5 shows projected liquid levels in a 87.5 M² bed
every month of the year, for 1995, given an input rate of 25,000 Liters
per month. The level peaks in January at a level about 15cm below the
surface, and the bed is virtually empty from August through October.

7.4 Safety Factors Included In ET Bed Sizing

The safety factors incorporated into bed sizing are as follows:\
The calculation method assumes the maximum liquid level in Puerto Ayora
would be about 30cm below the surface of the bed.\
The benefits of extra transpiration from the planting of shrubs has been
ignored. Planting shrubs could increase overall net daily evaporation by
25%, and are strongly advised to increase bed performance.\
Transpiration rates are based on plant activity in the first year only.
Rate of evaporation increases in subsequent years as the plants mature
have been ignored.

Transpiration rates for plants are based on grasses with known
evaporation rates in North Carolina which are dormant and less effective
in evaporative activity between October and March which is the rainy
season in Puerto Ayora and more rain water intrusion to the bed would
occur.

The daily evaporation rates for bacterial action are based on figures
from Miami, which is less temperate than Puerto Ayora, and thus less
effective in biological evaporative action.

Taken together these safety factors provide substantial reserves.
However, if input increases far above design capacity, the bed should be
extended in size.

**APPENDIX 1.**

**Natural Evaporation from the Saturated Sand Layer in the Bed**\
\
Everyone is familiar with evaporation, and how the amount of liquid
evaporated naturally varies with climate and the time of year. Figures
for average evaporation are available by month for all climatic zones in
North America. These figures are normally for \"Pan Evaporation\" which
is the amount of evaporation that will occur from a free standing
container of water.

In Puerto Ayora pan evaporation varies from 1.2mm (.047\") per day in
December to 3.3mm (.13\") per day in March.

 

[Table 4]{.underline}

Daily Pan Evaporation Rates By Month For Puerto Ayora, 1995

  ------------- ------ ----- ----- ----- ----- ----- ----- ------ ------ ----- ------ -----
                Jan    Feb   Mar   Apr   May   Jun   Jul   Aug    Sep    Oct   Nov    Dec

  mm/day        1.9    3.0   3.3   2.3   2.0   1.7   2.0   1.9    2.1    1.8   1.61   1.2

  Inches/day    .075   .12   .13   .09   .08   .07   .08   .075   .083   .07   .063   .05
  ------------- ------ ----- ----- ----- ----- ----- ----- ------ ------ ----- ------ -----

It is not so widely known that these pan evaporation figures can
increase dramatically if instead of having a container of water, the
liquid is contained in a semi saturated sand or fine crushed (1mm) lava
bed. In such a situation, liquid covers the surface of the grains of
material, and there is a very greatly increased contact area between air
and liquid. The increased evaporation which results, can also be
quantified. This increase, which can more than double pan evaporation
figures, varies with the depth of the liquid in the bed as shown in
Table 5 below.

[Table 5]{.underline}

\% Increase To Pan Evaporation With Waste Liquid At Different Levels
Below bed Surface

Down in cm

  -------- ------- ------ ------ ------ ------ ------ ------ ---- ------ ------ ------
  5        10      15     20     25     30     35     40     45   50     55     60

  +120%    +113%   +93%   +71%   +60%   +40%   +30%   +12%   0    -12%   -23%   -33%
  -------- ------- ------ ------ ------ ------ ------ ------ ---- ------ ------ ------

As an example, in Puerto Ayora in January, if the depth of liquid in the
bed was 5mm below the surface, then evaporation would increase from the
regular pan evaporation rate of 1.9mm (.075\") per day to 4.2mm (.165\")
per day. Evaporation rates for Puerto Ayora with waste levels 20cm down
in the bed are shown for each month on Table 6 below.

[Table 6]{.underline}

Assumed Daily Evaporation Rates By Month With Liquid 20cm Down In The
Sand Bed

(71% Better Than Straight Pan Evaporation)

  ------------- ------ ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- -----
                Jan    Feb   Mar   Apr   May   Jun   Jul   Aug   Sep   Oct   Nov   Dec

  mm/day        3.25   5.3   5.6   3.9   3.4   2.9   3.4   3.3   3.6   3.0   2.7   2.1

  Inches/day    .13    .20   .22   .15   .14   .11   .15   .13   .14   .12   .11   .08
  ------------- ------ ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- -----

**APPENDIX 2.**

**Transpiration From The Vegetation Planted In The Bed**

In order to grow, plants need to draw liquid in through their roots.
After use by the plant, excess liquid is transpirated, or given back to
the atmosphere, through the foliage.

Some plants transpirate much more than others, for example one corn
plant requires some 4.2 L (1.1 USG) per day during a Michigan growing
season, whereas a small maple tree would need about 65L (17 USG) per day
in New England.

Often a mixture of grass and shrubs proves to be the ideal vegetation
for an evapo-transpiration bed.

Transpiration volumes vary, not only with type of vegetation, but also
with the time of year, climatic zone, the amount of oxygen in the waste,
and the number of years the vegetation has been planted.

Transpiration figures using conservative assumptions of first year grass
only are shown below in table 7.

Dr. Mark Gardner of Estatión Científica Charles Darwin recommends the
use of Sedge (c*yperus lingularis and c. andersonii)* as native
materials, which would perform well as transpiration growth and which
are readily available and can be plug planted. He can also recommend the
best growing shrubs to use, which can increase bed evaporation by as
much as 25%.

[Table 7]{.underline}

Estimated Daily Transpiration Rates By Month Assuming only Grass Planted
(No Shrubs) with fully aerobic waste water. Figures vary with plants
having a dormant season Oct-Mar. which builds a safety factor into the
calculations for Puerto Ayora which has a more mild climate year round.

  ------------- ------- ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------
                Jan\*   Feb    Mar    Apr    May    Jun    Jul    Aug    Sep    Oct    Nov    Dec

  mm/day        2.0     2.1    3.2    4.5    4.5    4.3    4.1    3.9    3.7    2.7    2.3    2.1

  Inches/day    0.08    0.08   0.13   0.18   0.17   0.16   0.15   0.15   0.15   0.13   0.13   0.13
  ------------- ------- ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------

\*Based on South Carolina figures.

If 25-30 shrubs per 1000 sq. ft. were planted, figures would almost
double.

**APPENDIX 3**

**Evaporation from the Heat Generated by Bacterial Action in the Bed**

**& Totals for All Three Evaporation Effects.**

3.1 Evaporation from the Heat Generated by Bacterial Action in the Bed\
Bacterial action in the bed occurs naturally to oxidize organic material
and convert it to stable nutrients which can be taken up and used by
plants. This bacterial action releases heat energy which in turn
increases evaporation rates.

The amount of energy released will depend on a number of factors,
including the amount of dissolved oxygen in the excess liquid, and the
ambient temperature. The figures by month, assuming aerobic waste
liquid, is shown at Table 8. The slightly colder temperature in Miami
reduces the effectiveness of aerobic action which builds a buffer into
system calculations for Puerto Ayora.

 

[Table 8]{.underline}\
Daily Evaporation from Bacterial Action By Month In Miami For Aerobic
Waste Liquid.

  ------------- ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------
                Jan    Feb    Mar    Apr    May    Jun    Jul    Aug    Sep    Oct    Nov    Dec

  mm./day       3.3    3.3    3.3    3.4    3.4    3.5    3.5    3.5    3.5    3.4    3.3    3.3

  Inches/day    0.13   0.13   0.13   0.13   0.13   0.14   0.14   0.14   0.14   0.13   0.13   0.13
  ------------- ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------

3.2 Total Evaporation resulting From the Evaporation, Transpiration &
Bacterial Action\
Total amounts of liquids removed from the ET bed is the sum of natural
evaporation (Table 6), Transpiration (Table 7), and Bacterial Action
(Table 8). Table 9 below is the sum of these three tables, before taking
into account the negative impact of precipitation (See Appendix 4).

[Table 9]{.underline}\
Daily Total Evaporation/transpiration By Month for Puerto Ayora.

  ------------- ------ ------ ------ ------ ------ ------ ----- ------ ------ ----- ----- -----
                Jan    Feb    Mar    Apr    May    Jun    Jul   Aug    Sep    Oct   Nov   Dec

  mm./day       8.55   10.7   12.1   11.8   11.4   10.7   11    10.7   10.7   9.1   8.3   4.5

  Inches/day    .34    .41    .48    .46    .44    .41    .44   .42    .43    .38   .37   .34
  ------------- ------ ------ ------ ------ ------ ------ ----- ------ ------ ----- ----- -----

**APPENDIX 4**

**Negative Impact of Precipitation & Total Net evaporation**

4.1 Negative Impact of Precipitation\
The evapo-transpiration bed is also subject to precipitation in the form
of rain which has to be deducted from total evaporation/transpiration as
detailed in Table 9.

Infiltration of precipitation into the Recycling Bed can be minimized
somewhat by good bed design. As shown in the section on \"Building the
Recycling Bed\", the best approach is to build the bed with a small 6\"
dome in the middle so that a proportion of precipitation drains off.
Studies have shown that such a dome will, on average, allow only 70 % of
the precipitation to penetrate the bed. The negative impact of
precipitation obviously varies by climatic zone and month. The figures
for Puerto Ayora, 1995 are shown on Table 10.\
\
[Table 10]{.underline}

 

Average Daily Precipitation In Puerto Ayora By Month, for 1995, with
Penetration Rate Of 70%

 

<table style="width:100%;">
<colgroup>
<col style="width: 26%" />
<col style="width: 7%" />
<col style="width: 5%" />
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 5%" />
<col style="width: 6%" />
<col style="width: 5%" />
</colgroup>
<tbody>
<tr class="odd">
<td></td>
<td>Jan</td>
<td>Feb</td>
<td>Mar</td>
<td>Apr</td>
<td>May</td>
<td>Jun</td>
<td>Jul</td>
<td>Aug</td>
<td>Sep</td>
<td>Oct</td>
<td>Nov</td>
<td>Dec</td>
</tr>
<tr class="even">
<td><p>Total Precip.</p>
<p>mm/day</p></td>
<td>5.9</td>
<td>.30</td>
<td>1.3</td>
<td>.01</td>
<td>.04</td>
<td>.14</td>
<td>.44</td>
<td>.32</td>
<td>.86</td>
<td>.51</td>
<td>.16</td>
<td>.31</td>
</tr>
<tr class="odd">
<td>Infiltration (70%) mm/day</td>
<td>4.1</td>
<td>.21</td>
<td>.90</td>
<td>NA</td>
<td>.03</td>
<td>.09</td>
<td>.31</td>
<td>.22</td>
<td>.6</td>
<td>.35</td>
<td>.11</td>
<td>.22</td>
</tr>
<tr class="even">
<td>Infiltration (70%) inches/day</td>
<td>.16</td>
<td>NA</td>
<td>.03</td>
<td>NA</td>
<td>NA</td>
<td>NA</td>
<td>.01</td>
<td>NA</td>
<td>.02</td>
<td>.01</td>
<td>NA</td>
<td>NA</td>
</tr>
</tbody>
</table>

2.  Daily Total Net Evaporation by Month\
    By taking Total Evaporation/Transpiration figures (Table 9), and
    subtracting the amount of precipitation penetrating the bed (Table
    10), the Daily Total Net Evaporation performance of a Recycling Bed
    is determined. These performance figures are shown for Miami at
    Table 11.

[Table 11]{.underline}\
Daily Net Evaporation By Month

  ------------- ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------
                Jan    Feb    Mar    Apr    May    Jun    Jul    Aug    Sep    Oct    Nov    Dec

  mm/day        4.42   10.5   11.2   11.8   11.4   10.6   10.7   10.5   10.1   8.8    8.2    4.3

  Inches/day    0.18   0.40   0.45   0.46   0.44   0.41   0.43   0.42   0.41   0.37   0.37   0.34
  ------------- ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------

The above mm/day figures translate directly to Liters (L) per square
meter (m^2^) per day. Thus, for May a Bed of 1 m^2^ can evaporate 11.4
L/day in Puerto Ayora. To convert inches per day to US Gallons per
square foot, multiply by 0.62

**APPENDIX 5**

**Loading of 87.5 M² ET Bed with Input of 25,000 Liters/Month to
determine Liquid Levels by Month.**

To check the Bed sizing in the example in Item 7.3 above, the ET bed has
been loaded month by month to ensure that the levels in the bed are well
down in the bed throughout the year. Starting in the month of October,
the Table below shows that the level rises through to February and then
declines until by August the bed is virtually empty.

[Table 3]{.underline}

Utilization Of 87.5 M² Bed With Input 25,000 Liters/month

This table starts in October when it is assumed the bed would have no
carry over from the preceding months.

 

+----+-----------+----------+-----------+------------+--------------+
| Mt | 87.5 M²   |          |           |            |              |
| h. | bed       |          |           |            |              |
|    |           |          |           |            |              |
|    | Capacity  |          |           |            |              |
|    | 87.5 M² X |          |           |            |              |
|    | 60cm deep |          |           |            |              |
|    | (52.5 M³  |          |           |            |              |
|    | Approx.   |          |           |            |              |
|    | 52,500    |          |           |            |              |
|    | Liters)   |          |           |            |              |
+----+-----------+----------+-----------+------------+--------------+
|    | Ev        | Input    | ET        | Liters in  | \% Bed       |
|    | aporation |          | Surplus/  | Bed        | capacity     |
|    |           | Lite     |           | Cumulative | used         |
|    | Lit       | rs/Month | (deficit) | Surplus    |              |
|    | ers/Month |          |           | /(deficit) |              |
|    |           |          | Lit       |            |              |
|    |           |          | ers/Month |            |              |
+----+-----------+----------+-----------+------------+--------------+
| O  | 23,820    | 25,000   | (1,180)   | (1,180)    | 2%           |
| ct |           |          |           |            |              |
+----+-----------+----------+-----------+------------+--------------+
| N  | 21,525    | 25,000   | (3,475)   | \(4655\)   | 9%           |
| ov |           |          |           |            |              |
+----+-----------+----------+-----------+------------+--------------+
| D  | 11,663    | 25,000   | (13,337)  | (17,992)   | 34%          |
| ec |           |          |           |            |              |
+----+-----------+----------+-----------+------------+--------------+
| J  | 11,935    | 25,000   | (13,065)  | (31,057)   | 59%          |
| an |           |          |           |            |              |
+----+-----------+----------+-----------+------------+--------------+
| F  | 25,725    | 25,000   | 725       | (30,332)   | 58%          |
| eb |           |          |           |            |              |
+----+-----------+----------+-----------+------------+--------------+
| M  | 30,380    | 25,000   | 5,380     | (24,952)   | 47%          |
| ar |           |          |           |            |              |
+----+-----------+----------+-----------+------------+--------------+
| A  | 30,975    | 25,000   | 5,975     | (18,977)   | 36%          |
| pr |           |          |           |            |              |
+----+-----------+----------+-----------+------------+--------------+
| M  | 30,922    | 25,000   | 5,922     | (13,055)   | 25%          |
| ay |           |          |           |            |              |
+----+-----------+----------+-----------+------------+--------------+
| J  | 27,825    | 25,000   | 2,825     | (10,230)   | 19%          |
| un |           |          |           |            |              |
+----+-----------+----------+-----------+------------+--------------+
| J  | 29,024    | 25,000   | 4,024     | (6,206)    | 12%          |
| ul |           |          |           |            |              |
+----+-----------+----------+-----------+------------+--------------+
| A  | 28,481    | 25,000   | 3,481     | (2,725)    | 5%           |
| ug |           |          |           |            |              |
+----+-----------+----------+-----------+------------+--------------+
| S  | 26,512    | 25,000   | 1,512     | (1,213)    | 2%           |
| ep |           |          |           |            |              |
+----+-----------+----------+-----------+------------+--------------+

Note- These figures are based on 1995 weather data in which the annual
rainfall was 316mm, slightly higher than the median rainfall figure of
297mm. Rainfall at Puerto Ayora is cyclic with dry years followed by wet
years. The importance of the safety factors built into the calculations
are obvious, but during a bad El Nino cycle it is possible for the
system to overflow allowing partially treated effluent diluted with
rainwater to enter the aquifer. But even developed sewer systems and
standard leach fields fail with regular occurrence when flooded by El
Nino rains. With this system in place even during the worst El Nino year
when 9 times the mean rainfall fell, over 50% of the effluent will be
treated. When averaged with the dry year cycles this system will treat
almost all of the effluent through evapo-transpiration with out any
contact with groundwater.

**Reference-**

On-Site Recycling of Domestic Sewage in Florida,

By: C.M.Wilkinson Fall 1996, http://www.

Native Plant Reference from Dr. Mark Gardner, Estatión Científica
Charles Darwin, Santa Cruz, Galápagos, Ecuador

Weather Data from Estatión Científica Charles Darwin, Santa Cruz,
Galápagos, Ecuador

**Taking Care of Your Septic System**

-   Always conserve water to reduce the amount of wastewater that must
    be treated and disposed of.

-   Repair all leaking faucets and toilets.

-   Dispose of only biological wastes into the system.

-   Divert all down spouts, rainwater and other surface water away from
    the septic tank and disposal field.

-   Do not use your sink as a garbage disposal.

-   Do not put solvents, oils, paints, thinners, disinfectants,
    pesticides, etc. down the drain. This can disrupt the biological
    treatment method.

-   Do not dig in the evapo-transpiration bed, or build anything over
    the system.

-   Do not plant anything in the ET bed except native plants and shrubs.

-   Do not drive over the ET bed or compact it in any way.

**Please Do Not Flush the Following Items:**

paper towels

hair combings

fats, grease and oils

dental floss

gauze bandages

coffee grounds

condoms

disposable diapers

cigarette butts

kitty litter

tampons

sanitary napkins

panty liners

Line drawing of proposed ET bed construction is available at the
following-

![](media/image1.jpeg){width="4.75in"
height="6.25in"}<http://www.nps.gov/chis/septic.jpg>