City of Surrey, ND Municipal Infrastructure Needs Assessment September 2012 Project made possible by US Dept. of HUD Regional Substantiality Planning Grant and ND Energy Development Infrastructure and Impact Grant Fund programs
Summary of Needs Assessment The City of Surrey, located in Ward County, North Dakota, is experiencing a population increase due to energy development activities, with current proposed developments expected to increase the City s population from an estimated 950 people to 2,750 people within the next three years. The infrastructure needs assessment is intended as a high-level analysis and concept planning effort focused on key short-term infrastructure needs recommended to facilitate the anticipated growth and development. Table 1 summarizes the infrastructure needs assessment, proposed improvements, and opinion of costs included within this report. TABLE 1 SUMMARY OF INFRASTRUCTURE IMPROVEMENTS AND COST OPINION DESCRIPTION COST OPINION Water Distribution System Improvements 3,001,000 Wastewater Collection System Improvements 752,000 Wastewater Treatment System Improvements 5,669,000 Stormwater System Improvements 2,997,000 Street Improvements 1,889,000 TOTAL OPINION OF COST 14,308,000 Introduction In February 2012, the Vision West ND initiative was commenced to provide planning and technical assistance to a rapidly expanding 19-county area in western North Dakota. The primary goals of the Vision West ND project are to assist communities and counties in western North Dakota in addressing near-term needs to meet growth management challenges, and establish a diversified economy in the future through the development of local and regional strategic plans. Rapid population growth is exerting significant pressure on existing municipal water, sewer, and street systems, and in some cases, infrastructure expansion is necessary to support current and anticipated growth. Participating communities will receive a high-level infrastructure assessment to identify needs and prioritize infrastructure improvements, with opinions of probable costs by a professional engineering team. Building Communities, Inc. is the lead strategic planner engaged in the Vision West ND initiative and has subcontracted with Advanced Engineering & Environmental Services, Inc. (AE2S) to provide technical expertise regarding municipal infrastructure. This report includes brief infrastructure inventory, needs assessment, and opinions of probable costs for infrastructure improvements for the City of Surrey, North Dakota. The information used to City of Surrey Infrastructure Needs Assessment 2
prepare this assessment for the City of Surrey was compiled by AE2S during an interview with City of Surrey officials on May 2, 2012. COMMUNITY OVERVIEW The City recorded a population of 934 during the 2010 Census. The City s population from 1960 to 2010 has shifted between 309 and 999 with its previous population peak in 1980. The City, a bedroom community to the City of Minot, currently estimates its population at 1,069 based on 396 existing water and sewer accounts and an average of 2.7 people per household. This represents an increase of 14 percent in just over a year. The K-12 school enrollment has increased from 350 to 400 students in the last four to six years. Within the City s engineering analysis of existing infrastructure system and planned infrastructure improvements that maximize the existing infrastructure potential, the City would be positioned to accommodate an additional 3,196 people. Should this population growth become reality, the City would quickly move from the 55 th largest city in ND to within the top 15. Surrey City of Surrey Infrastructure Needs Assessment 3
CURRENT AND PLANNED DEVELOPMENT The current average occupancy rate in the City is 2.7 people per housing unit. Presently, there are known future development plans for an additional 557 residential housing units as indicated below. An assumption of up to an additional 1,000 housing units may be needed to account for future or presently unknown development plans. The pending developments are responding to a critical shortage of housing. These developments are awaiting the necessary infrastructure improvements of the City s water and wastewater systems, and developers are checking with City staff on a daily basis for updates to the status of these utility extensions. According to City Officials, future development plans that have been submitted to the City include the following: Silver Springs under construction 400 residential units Meyer 5 th Addition under construction 85 residential units Prairie Meadows Phase II 72 units apartments Silver Spring North recently annexed 480 Acres and rezoned to residential. No plat submitted yet The projected total service population of the City is estimated to increase from the present population of 1,060 people to as much as 2,750 people (more than double the current population) or 939 residential housing units if the projects listed above are constructed. In addition to the developments identified above, the City reported that a restaurant, commercial building, and a grocery store may be constructed in the near future. Other pending developments include Pheasant Hills residential development (approximately 200 units), Silver Springs North (approximately 1,000 units) and Eastland Park Estates (approximately 400 units). City of Surrey Infrastructure Needs Assessment 4
POTABLE WATER SYSTEM ASSESSMENT AND IMPROVEMENT RECOMMENDATIONS Water System Demands Based on the known development information and utilizing a future population estimate of 2,750 people, the average day domestic water demand is calculated as 140 gallons per day per capita (gpcd) resulting in an estimated water demand of 385,000 gallons per day (gpd). The 140 gpcd estimate is based on historic metered water usage. The maximum day demand is estimated by applying a peaking factor to the average day demand. The peaking factor in small communities in the region is estimated at 2.5. The corresponding estimated maximum day water usage is 962,500 gpd. Due to the size of the local school system, the fire flow demand has been estimated at 2,000 gallons per minute for a two hour duration, or a total of 240,000 gallons. Water Supply Description The City s water supply is provided by the North Prairie Rural Water System through an eight-inch line from the nearby Minot Water Treatment Plant. The City s current Water Purchase Agreement with North Prairie Rural Water System permits up to 3,000,000 gallons of water per month and meets all North Dakota Department of Health (NDDH) and federal water quality standards. Negotiations are underway to increase the water purchase agreement amount to 5,000,000 gallons per month. The City has also begun negotiations with North Prairie Rural Water to address service territories in the newly annexed areas. North Prairie Rural Water service territory is protected by Title 7, United States Code, Section 1926(b) which protect the rural water system territory from encroachment. Water Distribution and Storage Description With anticipated water storage demands of 192,500 gallons for domestic use and 240,000 gallons for fire flow requirements, the total water storage recommended is approximately 432,500 gallons. The City has an existing 50,000 gallon water tower as well as an additional 250,000 gallon underground storage tank at the connection of the North Prairie Rural Water System. The City meters individual users, and the current water rate is 23 per month for the first two thousand gallons, and 4.50 per thousand gallons thereafter. The water rate may be adjusted once the negotiations with North Prairie Rural Water System are settled. The City carries no long-term debt on the water system infrastructure. City of Surrey Infrastructure Needs Assessment 5
Water Supply Improvement Recommendations Assuming the City s current water storage is in good operable condition, a new water tower should be at least 182,500 gallons. Since water tank sizes are typically rounded to the nearest nominal tank size, the new elevated water tank should be about 250,000 gallons. While the City is in the process of negotiating an increase in their current contract with the water provider, the City s distribution system will need to be upgraded to meet the increase in water demand and fire flow. The City is proposing to install a new 12-inch water main from the existing underground reservoir to the new water tower. All the new developments will need to install minimum eight-inch water mains and 12-inch main connectors along section lines and quarter section lines. An opinion of the costs for the recommended improvements is presented in Table 2. It is also recommended that the City tests and evaluate the capacity if the pumping station at the reservoir once the new main is installed, and upsize the pumps if necessary. TABLE 2 OPINION OF PROBABLE COST WATER SYSTEM IMPROVEMENTS ELEVATED WATER TANK & WATER MAIN UPSIZE # DESCRIPTION QTY UNIT UNIT PRICE 1 TOTAL 1 250,000 Gallon Elevated Water Tank 1 Each 1,250,000 1,250,000 2 12" PVC - Class 150 C900 3,000 Feet 65 195,000 3 Street Replacement 4350 SY 60 261,000 4 Pump replacement 1 Each 150,000 150,000 Direct Construction Subtotal 1,856,000 Mobilization/Bonding/Insurance 8.00% 148,480 Traffic Control Lump Sum 25,000 Contingency 20.00% 371,200 Construction Subtotal (2012 dollars) 2,400,680 Engineering 20.00% 480,136 Legal & Administrative 5.00% 120,034 TOTAL 2 3,001,000 1 Estimated unit costs are based upon estimates from suppliers and recent bid tabs for similar projects 2 Estimates are rounded to nearest thousand City of Surrey Infrastructure Needs Assessment 6
WASTEWATER SYSTEM ASSESSMENT AND IMPROVEMENT RECOMMENDATIONS Existing System Description The City s wastewater system consists of a gravity collection system that drains to four lift stations which convey wastewater to a 34-acre, three-cell facultative lagoon system south of the City. The lagoon system is permitted to discharge by the NDDH, and historically has discharged twice a year. System Loading Based on the known development information submitted to the City, the future design population is estimated at 2,750. The average domestic wastewater flows generated are estimated at 339,660 gpd (235.7 gallons per minute (gpm)) based on 161 gpcd for the current population on the existing collection system (higher inflow and infiltration (I/I), and 100 gpcd for new collection system expansion. The future peak hour factor is assumed at 5.0, which is typical for small communities in this region. The peak flow is estimated to be 1,178 gpm. Collection System Existing Conditions and Deficiencies The existing wastewater collection system is constructed of vitrified clay pipe and PVC pipe. The collection system pipe sizes vary from four-inch to 12-inch. The existing northeast lift station was retrofitted in 2008, and the associated force main will be upsized in 2012. The southeast lift station is nearing capacity. The City is completing a redesign of the southwest lift station which will be replaced in spring 2013. The northwest lift station is under construction and will be operational before the end of 2012. Collection System Improvement Recommendations Because of the high I/I in the existing collection system, the City should consider retrofitting the existing system and replacing any damaged piping. Due to a lack of funding to complete these improvements, the City has elected not to pursue any sewer pipe rehabilitation at this time, but rather to focus on rehabilitating the existing southeast lift station and force main. An opinion of probable cost to rehabilitate the southeast lift station and forcemain is provided in Table 3. Treatment System Existing Conditions and Deficiencies Information from City staff, record drawings, and field data were used to assess the City s wastewater treatment capacity based upon the following factors: Primary Treatment Cell City of Surrey Infrastructure Needs Assessment 7
TABLE 3 OPINION OF PROBABLE COST WASTEWATER SYSTEM IMPROVEMENTS LIFT STATION & FORCE MAINREPLACEMENT # DESCRIPTION QTY UNIT UNIT PRICE 1 TOTAL 1 Lift Station 1 EA 250,000 250,000 2 10" Force Main 2000 LF 55 110,000 3 Emergency Generator/Electrical/I&C 1 EA 100,000 100,000 Direct Construction Subtotal 460,000 Mobilization/Bonding/Insurance 8.00% 36,800 Traffic Control Lump Sum 5,000 Contingency 20.00% 92,000 Construction Subtotal (2012 dollars) 593,800 Geotechnical Investigation 10,000 Engineering 20% 118,760 Legal & Administrative 5% 29,690 TOTAL 2 752,000 1 Estimated unit costs are based upon estimates from suppliers and bid tabs for similar projects throughout the region. 2 Estimates are rounded to the nearest thousand. Note: It is assumed that developers will bear the cost of sewer service lines to and within development areas. Total Biochemical Oxygen Demand (BOD) Loading Secondary Treatment and Holding Cells/Tertiary Cells The City s wastewater treatment system includes a series of three lagoon cells, one primary cell and two secondary cells. There is no pretreatment prior to the wastewater treatment system. The primary cell is designed as a stabilization lagoon with no active aeration. The purpose of the primary cell is to settle solids and reduce the BOD demands by means of a natural process utilizing the dissolved oxygen provided by the algae and natural aeration at the air-water interface. Typically, the primary cell would be designed to have a maximum water depth of five to six feet. The City s existing primary cell has a design water depth of five feet. This depth allows for sunlight to penetrate the water depth and promote algae growth. A minimum of two feet of water must be maintained in the cells at all times to limit vegetative growth on the cell bottom that could compromise the liner, prevent drying and cracking of the liner. The bottom two feet of the cells is also typically reserved for sludge accumulation. The surface area of the primary cell is 17.0 acres. City of Surrey Infrastructure Needs Assessment 8
The primary treatment cell depth is less than six feet and could be expanded from the current 15.3 million gallons to a total dischargeable volume of 30.0 million gallons. Utilizing the measured peak 180-day flow (during 2011 flooding) of 161 gpcd for the existing collection system and the Ten States Standard of 100 gpcd for the new collection system, the hydraulic load can accommodate a population equivalent (PE) of 1,092. The recommended BOD loading rate for primary cell for locations with an average winter temperature below 32 F is 30 pounds of BOD per acre per day. Based on the recommended loading rate, the City s primary cell can adequately serve a PE of 2,833. The recommended BOD loading rate for the overall acreage for locations with an average winter temperature below 32 F is 20 pounds of BOD per acre per day. Based on the recommended BOD loading rate, the City s overall system can adequately serve a PE of 3,778. Secondary treatment cells are intended to function as final settling basins, storage, and a location for treated wastewater discharges. The primary and secondary cells combined must have the storage capacity for 180 days of average flow. Secondary cells, as with the primary cells, must maintain a minimum water depth of two feet to prevent the cell liner from drying and cracking. The City s secondary cells (No. 2 and No. 3) each have a dischargeable volume of 7.35 million gallons, or total of 14.7 million gallons. The secondary cells are undersized to serve the current loads due to heavy I/I from the aging sanitary sewer collection system, as well as likely unpermitted connections of basement sump pumps and drain tiles to the system. The City wastewater treatment cells vary in the population each process can serve. A summary is provided in Table 4. TABLE 4 EXISTING WASTEWATER TREATMENT UNIT PROCESS SUMMARY UNIT PROCESS EXISTING SIZE/CAPACITY PE SERVED WITH EXISTING Primary Lagoon BOD Loading 17.0 acres 2,833 Total BOD Loading 34.0 acres 3,778 180-Day Hydraulic Loading 30.0 MG 1,091 According to a USGS Evaporation Study, evaporation in this area occurs at an average rate of approximately 28 inches per year. A weather gauging station in nearby Minot, North Dakota indicates the average annual precipitation is 17.2 inches per year. Net evaporation is estimated as 10.8 inches per year and the estimated evaporation from the lagoon per year is 10 million gallons. Evaporation accounts for about eight percent of the estimated annual flow. Evaporation does not account for City of Surrey Infrastructure Needs Assessment 9
water loss. Note that the evaporation occurs predominately in the summer; therefore, the winter months provide little benefit from evaporation. The NDDH regulations have a seepage limit of 1/8-inch per day. Available information states that the existing lagoon has a clay liner to minimize ground infiltration. NDDH regulations do not allow rapid infiltration basins as a means of discharging wastewater to groundwater, but allow treated effluent to be discharged to a surface body or drainage. It appears the wastewater system serving the City unintentionally discharges effluent to groundwater. Currently, the City holds a discharge permit allowing discharge from the lagoons to Class III waters. The current wastewater rates are 20.00 per month. There is no long-term debt associated with the City s wastewater system. Wastewater Treatment System Improvement Recommendations The existing primary lagoon cell is sufficient to handle the anticipated growth, but the secondary lagoon cells need to be expanded to provide additional storage to meet the design criteria. The proposed treatment system improvements are sized based on the primary lagoon BOD loading rate, the total system BOD loading rate, and the 180-day storage volume requirement. All three evaluation criteria should be met for successful wastewater treatment; therefore, the most restrictive of these criteria controls the evaluation. Additionally, disinfection is required, which happens naturally with adequate retention time due to pathogen die-off. The wastewater treatment system improvement recommendations include: Acquisition of 35 acres, and secure a purchase option on an additional 35 acres Construction of a 35-acre third secondary lagoon cell The opinions of probable cost for the improvements are shown in Table 5. STORMWATER SYSTEM ASSESSMENT AND IMPROVEMENT RECOMMENDATION The City does not own or utilize stormwater system infrastructure. Stormwater is currently conveyed from roads to swales, and into a slough system that eventually drains to a nearby river. The need for a drainage study to evaluate the existing drainage patterns has reportedly been a top priority for the City. The City is anticipating the construction of detention ponds within the system to offset the increased runoff as result of new developments. An opinion of probable cost for detention ponds is provided in Table 6. City of Surrey Infrastructure Needs Assessment 10
TABLE 5 OPINION OF PROBABLE COST WASTEWATER SYSTEM IMPROVEMENTS LAGOON SYSTEM EXPANSION # BID ITEM QTY UNITS UNIT PRICE 1 TOTAL 1 Excavation 66,293 CY 10.00 662,930 2 Embankment 66,293 CY 10.00 662,930 3 Clay Liner (imported) 55,295 cy 20.00 1,105,900 4 12" Riprap 4,034 SY 45.00 181,530 5 Geotextile Fabric 5,687 SY 3.00 17,061 6 Finish Grading/Seeding 5000 SY 5.00 25,000 7 Access Road 8,287 SY 25.00 207,175 8 14" Gravity Pipe 2,000 lf 75.00 150,000 9 14" Gate Valves 5 EA 2,100.00 10,500 10 Splash Pads 2 EA 1,000.00 2,000 11 Fence 6000 LF 8.00 48,000 Direct Construction Subtotal 3,073,026 Mobilization/Bonding/Insurance 8.0% 245,842 Traffic Control Lump Sum 10,000 Contingency 20.0% 614,605 Construction Subtotal (2012 dollars) 3,943,473 Land Acquisition 70 acres @ 10,000 700,000 Right-of-Way & Permits 25,000 Geotechnical Investigation 15,000 Engineering 20% 788,695 Legal & Administrative 5% 197,174 TOTAL 2 5,669,000 1 Estimated unit costs are based on estimates from suppliers and recent bid tabs for similar projects throughout the region. 2 Costs are rounded to nearest thousand STREET ASSESSMENT AND IMPROVEMENT RECOMMENDATIONS The City s street system includes paved streets with intermittent gravel streets. The main north/south thoroughfare is Pleasant Avenue, and the main east/west thoroughfare is Second Street. Ward County partially maintains both main thoroughfares. Due to the increase in construction activity and the age of the streets, problems are beginning to occur throughout town. The City has implemented a truck traffic ordinance to minimize the impact of the significant increase in traffic. City of Surrey Infrastructure Needs Assessment 11
# BID ITEM QTY UNITS UNIT PRICE 1 TOTAL 1 Excavation & Embankment 65,000 CY 20.00 1,300,000 4 12" Riprap 4,000 SY 45.00 180,000 5 Geotextile Fabric 5,500 SY 3.00 16,500 6 Finish Work/Seeding 5000 SY 5.00 25,000 7 Access Road 8,300 SY 25.00 207,500 8 24" Gravity Pipe 750 lf 75.00 56,250 10 Outfall 3 EA 1,000.00 3,000 11 Fence 6000 LF 8.00 48,000 Direct Construction Subtotal 1,836,250 Mobilization/Bonding/Insurance 8.0% 146,900 Traffic Control Lump Sum 15,000 Contingency 20.0% 367,250 Construction Subtotal (2012 dollars) 2,365,400 Right-of-Way & Permits 25,000 Geotechnical Investigation 15,000 Engineering 20% 473,080 Legal & Administrative 5% 118,270 TOTAL 2 2,997,000 1 Estimated unit costs are based on estimates from suppliers and recent bid tabs for similar projects throughout the region. 2 Costs are rounded to nearest thousand TABLE 6 OPINION OF PROBABLE COST STORMWATER SYSTEM IMPROVEMENTS DETENTION PONDS Street System Improvement Recommendations Based upon preliminary review and discussions with the City staff, the recommended improvements include mill and overlay of approximately 6,000 linear feet of streets, and reconstruction of approximately 2,400 linear feet of the existing City streets. It is further recommended that a street assessment be completed in the near-term to develop a city-wide street improvement plan to address the shortfalls of the existing infrastructure before the end of 2014. The opinion of probable cost for the recommended improvements is shown in Table 7. City of Surrey Infrastructure Needs Assessment 12
TABLE 7 OPINION OF PROBABLE COST STREET IMPROVEMENTS # DESCRIPTION QTY UNIT UNIT PRICE 1 TOTAL 1 Milling Asphalt Surface 25,000 SY 7.00 175,000 2 1.5 inch overlay (asphalt) 25,000 SY 15.00 375,000 3 Full Depth Asphalt Repair 10000 SY 53.00 530,000 4 Adjust Gate Valve Box 25 EA 850.00 21,250 5 Adjust Manhole Casting 40 EA 1,200.00 48,000 Direct Construction Subtotal 1,149,250 Mobilization/Bonding/Insurance 8.00% 91,940 Traffic Control Lump Sum 40,000 Contingency 20% 229,850 Construction Subtotal (2012 dollars) 1,511,040 Engineering 20% 302,208 Legal & Administrative 5% 75,552 TOTAL 3 1,889,000 1 Estimated unit costs are based upon estimates from suppliers and bid tabs for similar projects throughout region. 2 The ENR 20 year average Construction Cost Index is +3.1% (as of November 2009), so capital costs are projected to an anticipated construction date in 2014 using an annual 3.1% inflation rate. 3 Estimates are rounded to nearest thousand CONCLUSION In conclusion, the City will need to implement approximately 14.3 million in water, wastewater, stormwater, and street infrastructure improvements to address current deficiencies and meet pending development demands. The necessary improvements include a new water tower and water mains, expansion of the existing facultative lagoon system, replacement of the existing southeast lift station, installation of a stormwater management basins, and street repair and overlays. The work that provided the basis for this publication was supported by funding under an award with the U.S. Department of Housing and Urban Development. The substance and findings of the work are dedicated to the public. The author and publisher are solely responsible for the accuracy of the statements and interpretations contained in this publication. Such interpretations do not necessarily reflect the views of the Government. City of Surrey Infrastructure Needs Assessment 13