1 Prepared by Yakima County Public ServicesRCIM Prepared by Yakima County Public Services
2 CATEGORIES Residential onsite Sewage Systems (ROSS)Large Onsite Sewage Systems (LOSS) Commercial Onsite Septic Systems (COSS) Residential Lawn Fertilizers Small Scale Commercial and Hobby Farms
3 ROSS – Data 6,044 Households Utilize ROSSAverage Household Size Range = 2.72 to 4.16 persons per household (OFM 2010) Approximate Location of each ROSS Determined – (GIS) Soil Type at Approximate Location Determined – (NRCS 2014) Land Elevation Determined – (GIS Land Elevation Model) Approximate Depth to Groundwater Determined (USGS – Vaccaro el al. 2009)
4 ROSS – Data Inputs TN Loading to a ROSS Ranges from 6 to 17 grams per person per day (EPA 2002a and 1992) Low - 6 gm/cap/day Medium gm/cap/day High – 17 gm/cap/day Denitrification - the conversion of nitrates into nitrogen gas which is then released into the atmosphere. This is caused by bacteria and is dependent upon environmental conditions existing in the soils below a drain field GWMA soils are predominately sands, silts, silty loams and clay loams (GIS and NRCS). These soils are favorable for denitrification (EPA 2002a) Denitrification requires Aerobic (unsaturated) soil conditions – The depth to groundwater at over 90% of GWMA ROSS locations is greater than 10 feet (GIS and Vaccaro et al. 2009).
5 ROSS – Data Inputs (continued)Denitrification (continued) Denitrification amounts are difficult to predict. Studies have shown that 10% to 40% of TN can be removed (EPA 2002a) Most common removal rates are between 10% and 20% Conservative Denitrification rates used in study: Low – 20% Medium 15% High 10%
6 ROSS – Data Inputs (continued)Septage Removal – the periodic pumping of septic tanks removes some TN from entering the drain field Average TN in septage is 588 mg/l (EPA 1994) Minimum tank size = 900 gallons (WAC A-0010) TN in tank when “full” = 4.4 pounds (2Kg) Recommended Pumping Frequency every 3 to 5 years 82% responded to Well Assessment Survey that they have their tank pumped regularly Report uses conservative pumping frequency Low – every 3 years Medium – every 5 years High – every 10 years
7 ROSS – Data Input SummaryParameter Units Low Medium High Household Size Persons / Household Census Tract Average TN Loading to OSS gm/person/day 7 11.2 17 Denitrification Percent 40 25 10 Septic Tank Size Liters 3,407 TN in Septage gm/L 0.588 TN in Septic Tank When Pumped gm 2,003 Septic Tank Pumping Frequency Years 3 5
8 ROSS – Data Output SummaryUnits TN Generated by 6,044 Households Denitrification Average Annual TN Removed by Pumping Total N LOW Grams/Year 54,636,835 (10,927,367) (4,035,377) 39,674,091 Lbs/Year 120,454 (24,091) (8,896) 87,466 Tons/Year 60.23 (12.05) (4.45) 43.73 MEDIUM 87,418,937 (13,112,840) (2,421,226) 71,884,870 192,726 (28,909) (5,338) 158,479 96.36 (14.45) (2.67) 79.24 HIGH 132,689,457 (13,268,946) (1,210,613) 118,209,898 292,530 (29,253) (2,669) 260,608 146.27 (14.63) (1.33) 130.30
9 Migrant Population Effect on ROSSAg Producers Supplement their workforce with migrant workers during peak periods ROSS calculations are for permanent residents only. A migrant worker is defined as a farm worker whose employment requires travel that prevented the worker from returning to his/her permanent place of residence the same day (USDA NASS 2014) In 2012 there were 9,598 migrant workers employed by agriculture throughout all of Yakima County (USDA NASS 2014). Prorating the number of migrant workers by crop acres county-wide results in a GWMA migrant worker population of 2,687 migrant workers (28% of county total) Annualized migrant population = 224 full time persons (assumed to reside in GWMA area) Adds low, medium, and high TN loading of 0.5, 0.9, and 1.4 tons per year
10 ROSS Loading per Acre Estimated area for all GWMA ROSS = 398 acresBased on NRCS soil type and corresponding DOH infiltration rate at each drainfield Based on a design flow of 60 gallons per person per day using household size at each drainfield Based on infiltration trenches 1’ wide, 60’ long, 5’ lateral separation Based on ROSS TN loading calcualtions Results: Low – 223 pounds per acre Medium – 403 pounds per acre High – 662 pounds per acre
11 LOSS Data Two LOSS within GWMA AreaZillah LOSS – Large fruit packing operation and warehouse Operates 12 months per year Design capacity – 5,000 gallons per day TN Loading predominately human waste – TN loading = 8.7 gm/cap/day and water use = 16.2 gal/cap/day (EPA1992) WDOH design criteria results in capacity = 103 persons Results using ROSS methodology Low – 575 pounds per year (0.29 tons/year) Medium – 612 pounds per year (0.31 tons per year) High – 649 pounds per year (0.32 tons per year)
12 LOSS Data (continued) Granger LOSS – Temporary Migrant HousingOperates 1month per year Design capacity – 4,850 gallons per day TN Loading assumed equivalent to ROSS loading WDOH design criteria results in capacity = 27 persons Results using ROSS methodology Low – 9.0 pounds per year Medium – 16.0 pounds per year High – 27.0 pounds per year
13 LOSS Output Summary Low Medium High Loading (lb N/acre) 195 209 225Low Medium High Loading (lb N/acre) 195 209 225 Loading (kg N/hectare) 218 235 252 Total loading (ton N/year) 0.29 0.31 0.34 Total loading (kg N/year) 265 285 307
14 COSS Data COSS – refers to septic systems used for employees working at Ag businesses that operate year-round and are not classified as LOSS by WDOH 52 CAFOs classified by herd size (WSDA) Number of employees based on herd size using ratio of cows to employees (Reed 1994) Equates to 869 full time employees TN = 8.7 gm/cap/day and water usage = 16.2 gallons/cap/day TN Loading Using ROSS methodology Low – 2.43 tons per year Medium – 2.59 tons per year High – 2.74 tons per year
15 Residential Lawn Fertilizer“Green” areas (grass, trees, shrubs) representing areas where fertilizer may be applied were determined using GIS and infrared orthophotography Using the green layer, four representative areas within the GWMA were examined to determine the percentages of land area that were green. Each of the areas were one square mile in size and the buildings and crop lands were subtracted from the green areas. Urban – within City of Sunnyside Suburban – Outside City of Sunnyside, but within Sunnyside Urban Growth Boundary Rural High Density – within Outlook Rural Low Density – within County with large parcels
16 Residential Lawn Fertilizer (continued)Assumes the use of a fertilizer applied once each year equates to 23.3 pounds/acre of nitrogen per year Assumes a high, medium, and low percentage of residents who fertilize to be 80, 50, and 20 % respectively Assumes no nitrogen lost to plant uptake, denitrification, or volatization
17 Residential Lawn Fertilizer (continued)Representative Area Application Green Area per Parcel (acres) Number of Parcels Green Area in GWMA (acres) Urban All parcels located in incorporated cities 0.09 7,180 646 Suburban All parcels located in UGA outside of cities 1.25 892 1115 Rural high density All rural parcels <= 5 acres 0.64 3,285 2102 Rural low density All rural parcels > 5 acres 0.73 709 518 Totals 12,066 4,381
18 Residential Lawn Fertilizer (continued)Low Medium High Loading (lb N/acre) 4.7 11.7 18.6 Loading (kg N/hectare) 5.2 13 20.9 Total loading (ton N/year) 10.2 25.5 40.8 Total loading (kg N/year) 9,260 23,152 37,043
19 Small Scale Commercial and Hobby Farms -DataRefers to residential land uses other than lawns that may contribute nitrogen to the GWMA area Includes residential parcels < 10 acres in size that are not included in WSDA’s crop inventory Lawn areas and building footprints were deducted Fertilizer application rates based on RCIM Workgroup recommendations Assumes a high, medium, and low percentage of residents who fertilize to be 80, 50, and 20 % respectively
20 Small Scale Commercial and Hobby Farms –Data (continued)Parcel Size Range of Small-Scale Farm (acres) Number of Parcels Total Parcel Area (acres) Lawn Area (acres) Building 2,000 sf/parcel (acres) Effective Area (acres) 0 to 2.5 2335 2,481.5 1,804.1 107.2 570.2 2.51 to 5.0 311 1,075.6 223.0 14.3 838.4 5.1 to 10.0 110 776.1 83.3 5.1 687.7 Totals 2756 4,333.2 2,110.4 126.5 2,096.3
21 Small Scale Commercial and Hobby Farms –Data (continued)Parcel Size of Small-Scale Farm (acres) Nitrogen Fertilizer Application (lb/acre/yr) Nitrogen Fertilizer Application (kg/hectare/year) 0 ≤ 2.5 14 15.7 2.51 ≤ 5.0 21 23.5 5.01 < 10.0 28 31.4
22 Small Scale Commercial and Hobby Farms –Data (continued)Parcel Size of Small-Scale Farm Small-Scale Farm Effective Area (acres) Application (lbs) TN Low at 20% (tons) TN Medium at 50% (tons) High at 80% (tons) 0 ≤ 2.5 Acres 570.2 14 0.80 2.00 3.19 2.51 Acres ≤ 5.0 Acres 838.4 21 1.76 4.40 7.04 5.01 Acres ≤ 10.0 Acres 687.7 28 1.93 4.81 7.70 Total (ton N/year) 4.48 11.21 17.94 (kg N/year) 4,068 10,171 16,273