15.42.060 Approval standards | Bellingham Municipal Code

15.42.060 Approval standards.

A. New Development Requirements. All new development shall provide protection for the quality of the waters of the state of Washington by the application of best management practices and/or source controls.

All new development that requires either a building permit which results in 300 square feet or more of hard surface area or has a land disturbance area greater than 500 square feet shall at a minimum comply with Minimum Requirement No. 2 within subsection (F) of this section, all other applicable federal, state, and local ordinances, codes and regulations for stormwater management, and shall obtain a stormwater permit from the city of Bellingham prior to commencement of activity. In addition, new development that exceeds certain other thresholds, as further identified herein, shall be required to comply with additional minimum requirements as follows:

1. The following new development shall comply with Minimum Requirements No. 1 through No. 5 within subsection (F) of this section:

a. New single-family homes or duplexes; or

b. Developments that create or add 2,000 square feet, or greater, of new, replaced, or new plus replaced hard surface area; or

c. Land-disturbing activity of 5,000 square feet or greater; or

d. A subdivision, or the lots created from a subdivision, that contains two or fewer lots and is not likely to exceed the land disturbance and/or hard surface thresholds from future property development; or

e. Developments within the Lake Whatcom watershed that create or add 120 square feet or greater, of new, replaced or new plus replaced hard surface area; or

f. Land-disturbing activity within the Lake Whatcom watershed of 500 square feet or greater; or

g. Other development that is determined by the public works director to contain a significant risk for the degradation of stormwater.

2. The following new development shall comply with Minimum Requirements No. 1 through No. 9 within subsection (F) of this section:

a. Creation or addition of 5,000 square feet, or more, of new, replaced or new plus replaced hard surface area; or

b. Convert three-fourths acres, or more, of native vegetation to lawn or landscaped areas; or

c. Convert two and one-half acres, or more, of native vegetation to pasture; or

d. One acre or more of land-disturbing activity; or

e. A subdivision containing two or more lots that is likely to exceed the land disturbance and/or hard surface thresholds from future property development; or

f. Other development that is determined by the public works director to contain a significant risk for the degradation of stormwater.

3. Lake Whatcom New Development. In addition to the requirements for new development under subsections (A)(1) and (2) of this section, all new development that drains to Basin One of Lake Whatcom, as shown in BMC 15.42.020, that is subject to Chapter 16.80 BMC, Lake Whatcom Reservoir Regulatory Provisions, and that creates or replaces more than 300 square feet of hard or partially pervious surface shall provide for stormwater management as follows:

a. An engineered stormwater site plan shall be provided, for review and approval, which determines site-specific controls to limit stormwater runoff and phosphorus transport from the total site to levels associated with a predeveloped forested condition. The plan shall at a minimum provide soils reports, ground water studies, hydrologic analyses, appropriate BMPs and BMP maintenance plans to demonstrate the ability to meet this code. Additionally all stormwater site plans shall maintain or create a minimum of 30 percent “natural forested condition” upon the site per Chapter 16.80 BMC.

Any BMP or combination of BMPs will be considered that would lead to successful management of flow and phosphorus transport. Developed flow shall meet the forested flow duration standards of this code and the Ecology Manual. Phosphorus transport through surface flow or interflow shall be limited to an average discharge of no more than 0.15 pounds/acre/year; or

b. If the site has retained or created 75 percent or more of forested/native vegetation on a site per Chapter 16.80 BMC and the site will not exceed 2,000 square feet of hard surfaces or up to 20 percent of the total site, whichever is the lesser, and the site will also not exceed 1,000 square feet of partially pervious surfaces as defined within Chapter 16.80 BMC or up to 10 percent of the total site, whichever is the lesser. And the total of hard surfaces and partially pervious surfaces will not together exceed 25 percent of the total site area nor exceed 2,500 square feet.

If these conditions can be met, stormwater mitigation for the site shall require compliance to the maximum extent practicable with on-site water management BMPs as provided for in the manual; or

4. If the site development creates or replaces more than 120 square feet and less than 300 square feet of hard or partially pervious surfaces and the addition of said surfaces does not cause the property to be in noncompliance with the limits on such surfaces through Chapter 16.80 BMC, the site shall provide mitigation for stormwater and phosphorus transport at the rate of 10 square feet of mitigation for every one square foot of creation or replacement of these surfaces.

Hard surfaces developed under this method shall at a minimum be mitigated to the standard provided for by an on-site stormwater management plan as provided in the Ecology Manual.

Mitigation of partially pervious surfaces shall at a minimum be by way of lawn removal; or other method approved by the city.

5. Construction of phosphorus limiting or flow limiting projects may be permitted outright with a no fee stormwater permit upon review of the facilities for compliance with Lake Whatcom management standards.

6. Gardening and landscape practices that are contained within one or more areas of a property and the total square footage of all areas together do not exceed five percent of the property or 500 square feet, whichever is the greater, are considered exempt gardens. Exempt gardens shall be maintained and located to prevent runoff resultant from direct precipitation, water run-on and irrigation. Exempt garden areas are not exempt from the prohibition on the use of phosphorus-containing products including fertilizers, pesticides or other deleterious materials. Landscape or gardening areas beyond the limit provided herein, and which do not meet definition of phosphorous or flow-limiting BMPs as defined in this chapter, are considered to be partially pervious surfaces and subject to the limitations and requirements of Chapters 15.42 and 16.80 BMC regarding those areas. Exempt gardens that are not in active use for gardening or landscaping purposes for more than 30 days shall provide for the stabilization of the exempt garden by the use of a Type 1 mulch or other approved method.

B. Redevelopment Requirements. All redevelopment shall provide protection for the quality of the waters of the state of Washington by the application of best management practices and/or source controls.

All redevelopment that requires either a building permit which results in 300 square feet or more of hard surface area or has a land disturbance area greater than 500 square feet shall at a minimum comply with Minimum Requirement No. 2 within subsection (F) of this section, all other applicable federal, state, and local ordinances, codes and regulations for stormwater management and shall obtain a stormwater permit from the city of Bellingham prior to commencement of activity. In addition, all redevelopment that exceeds certain thresholds, as further identified herein, shall be required to comply with additional minimum requirements as follows:

1. The following redevelopment shall comply with Minimum Requirements No. 1 through No. 5 within subsection (F) of this section:

a. The new, replaced, or total of new plus replaced hard surfaces is 2,000 square feet or more, or 5,000 square feet or more of land-disturbing activities; or

b. A subdivision, or the lots created from a subdivision, that contain two or fewer lots and is not likely to exceed the land disturbance and/or hard surface thresholds from future property development; or

c. Any redevelopment within the Lake Whatcom watershed that creates or adds 120 square feet or greater of new, replaced or new plus replaced hard surface area; or

d. Any land-disturbing activity within the Lake Whatcom watershed of 500 square feet or greater; or

e. Other development that is determined by the public works director to contain a significant risk for the degradation of stormwater.

2. The following redevelopment shall comply with Minimum Requirements No. 1 through No. 9 within subsection (F) of this section:

a. Creation or addition of 5,000 square feet, or more, of new, replaced or new plus replaced hard surface area; or

b. Converts three-fourths acres, or more, of native vegetation to lawn or landscaped areas; or

c. Converts two and one-half acres, or more, of native vegetation to pasture; or

d. One acre or more of land-disturbing activity; or

e. A subdivision containing two or more lots that is likely to exceed the land disturbance and/or hard surface thresholds from future property development; or

f. Other development that is determined by the public works director to contain a significant risk for the degradation of stormwater.

3. Lake Whatcom Redevelopment. In addition to the requirements for redevelopment under subsections (A)(1) and (2) of this section, all redevelopment that drains to Basin One of Lake Whatcom, as shown in BMC 15.42.020, and that is subject to Chapter 16.80 BMC, Lake Whatcom Reservoir Regulatory Provisions, and that creates or replaces more than 300 square feet of hard or partially pervious surface, shall provide for stormwater management as follows:

b. If the total site has retained or will create 75 percent or more of forested/native vegetation on the site per Chapter 16.80 BMC, and will contain less than 2,000 square feet of hard surfaces, and will not exceed 20 percent hard surfaces on the site, and will contain less than 1,000 square feet of partially pervious surfaces, and will not exceed 10 percent partially pervious surfaces, and the total of hard surfaces and partial pervious surfaces will not exceed 25 percent of the total site area nor will it exceed 2,500 square feet of those combined surfaces; and

If the hard surfaces developed under this method are mitigated to the standard provided for by an on-site water management plan as provided for in this chapter;

Then, the total site development shall be considered to comply fully with stormwater standards; or

4. If the site redevelopment creates or replaces more than 120 square feet and less than 300 square feet of hard or partially pervious surfaces and the addition of said surfaces does not cause the property to be in noncompliance with the limits on such surfaces through Chapter 16.80 BMC, the site shall provide mitigation for stormwater and phosphorus transport at the rate of 10 square feet of mitigation for every one square foot of creation or replacement of these surfaces.

Hard surfaces developed under this method shall at a minimum be mitigated to the standard provided for by an on-site stormwater management plan as provided in the Ecology Manual.

Mitigation of partially pervious surfaces shall at a minimum be by way of lawn removal or other method approved by the city.

C. If the runoff from the new impervious surfaces and converted pervious surfaces is not separated from runoff from other surfaces on the project site, the stormwater treatment facilities must be sized for the entire flow that is directed to them.

D. On a case-by-case circumstance, the minimum requirements in subsection (F) of this section may be met for an equivalent (flow and pollution characteristics) area within the same site. For public road projects, the equivalent area does not have to be within the project limits, but must drain to the same receiving water. Approval of equivalency shall be determined by the public works director or his assignee.

1. For road-related projects, except for projects that drain to Basin One of Lake Whatcom, runoff from the replaced and new hard surfaces (including pavement, shoulders, curbs, and sidewalks) and the converted vegetation areas shall meet all the minimum requirements if the new hard surfaces total 5,000 square feet or more and total 50 percent or more of the existing hard surfaces within the project limits. The project limits shall be defined by the length of the project and the width of the right-of-way.

2. Replaced surfaces may be allowed to be mitigated differently than new surfaces. When required to comply with the forested standard of Minimum Requirement No. 7 in subsection (F) of this section, only 50 percent of the replaced surfaces must be mitigated to comply with the forested standard. The remaining 50 percent of the replaced surfaces may either be considered in the forested condition or if desirous, may be considered in the condition existing as of September 1, 1995, as may be determined using aerial photography or other means acceptable to the city.

3. Other types of redevelopment projects, except for projects that drain to Basin One of Lake Whatcom, shall comply with Minimum Requirements No. 1 through No. 9 for the new and replaced hard surfaces and the converted vegetation areas if the total of new plus replaced hard surfaces is 5,000 square feet or more, and/or the valuation of proposed improvements – including interior improvements – exceeds 50 percent of the assessed value of the existing site improvements.

4. Those projects that meet the definition of redevelopment, only 50 percent of replaced surfaces shall be required to comply with the forested standard of Minimum Requirement No. 7 in subsection (F) of this section. The remaining 50 percent of the replaced surfaces may either be considered in the forested condition or if desirous, may be considered in the condition existing as of September 1, 1995, as may be determined using aerial photography or other means acceptable to the city.

5. Underground utility projects that replace the ground surface with in-kind material or materials with similar runoff characteristics are not subject to redevelopment requirements except construction site erosion control.

F. Minimum Requirements for Stormwater Mitigation. The following are considered the minimum requirements for stormwater mitigation:

1. Minimum Requirement No. 1 – Preparation of Stormwater Site Plans (“SSP”). All projects meeting the thresholds in subsection (A)(1) or (2) of this section shall prepare a stormwater site plan (“SSP”) for the city’s review. SSPs shall be prepared in accordance with the current editions of the Ecology Manual, the city of Bellingham “Development Guidelines and Improvement Standards” and this BMC. This SSP may be incorporated with building, grading or clearing plan sets as applicable. Those projects that are subject to Minimum Requirements No. 1 through No. 9 shall include an engineering report that addresses all elements and minimum requirements of the project’s stormwater management along with an analysis that supports the SSP and the construction stormwater pollution prevention plan (“construction SWPPP”). If the project included construction of conveyance systems, treatment facilities, flow control facilities, structural source control BMPs, bioretention facilities, permeable pavement, vegetated roofs, a rainwater harvest system, and/or newly planted or retained trees for which a flow reduction credit was taken, the applicant shall submit a corrected plan (“record drawings”) to the local government agency with jurisdiction when the project is completed. These should be engineering drawings that accurately represent the stormwater infrastructure of the project as constructed. These corrected drawings must be professionally drafted revisions that are stamped, signed, and dated by a licensed civil engineer registered in the state of Washington.

a. All new development and redevelopment shall comply with construction SWPPP Elements No. 1 through No. 13 as described in this section below.

b. Projects outside the Lake Whatcom watershed in which the new, replaced, or new plus replaced hard surfaces total 2,000 square feet or more, or disturb 5,000 square feet or more of land must prepare a construction SWPPP as part of the stormwater site plan (see subsection (F)(1) of this section). Each of the 13 elements must be considered and included in a construction SWPPP unless site conditions render the element unnecessary and the exemption from that element is clearly justified in the narrative of the SWPPP. The SWPPP shall include, at a minimum, the narrative, the stormwater site plan and copies of best management practice detail sheets that will be utilized as a part of the SWPPP.

c. Projects outside the Lake Whatcom watershed that add or replace less than 2,000 square feet of hard surface and disturb less than 5,000 square feet of land are not required to prepare a construction SWPPP. They must, however, consider all of the 13 elements of construction stormwater pollution prevention detailed below and propose controls for all elements that pertain to the project site within the stormwater site plan.

d. Those projects, that are within the Lake Whatcom watershed, that create or add 200 square feet or greater, of new, replaced or new plus replaced hard surface area or that disturb more than 500 square feet of land shall provide a construction SWPP plan and a stormwater site plan as described above.

i. Element 1 – Preserve Vegetation/Mark Clearing Limits. Prior to beginning land-disturbing activities, including clearing and grading, all clearing limits, sensitive areas and their buffers, and trees that are to be preserved within the construction area should be clearly marked, both in the field and on the plans, to prevent damage and off-site impacts. Plastic, metal, or stake wire fence may be used to mark the clearing limits. Retain the duff layer, native top soil, and natural vegetation in an undisturbed state to the maximum degree practicable.

(A) Construction vehicle access and exit shall be limited to one route if possible.

(B) Access points shall be stabilized with quarry spall or crushed rock to minimize the tracking of sediment onto public roads.

(D) Public roads shall at a minimum be cleaned thoroughly at the end of each day. Sediment shall be removed from roads by shoveling or pickup sweeping and shall be transported to a controlled sediment disposal area. Street washing will be allowed only after sediment is removed in this manner.

(E) Street wash wastewater shall be controlled by pumping back on site, or otherwise be prevented from discharging into systems tributary to state surface waters.

(F) Control street wash wastewater by pumping back on site, or otherwise prevent it from discharging into systems tributary to waters of the state.

(A) Protect properties and waterways downstream of development sites from erosion and the associated discharge of turbid waters due to increases in the velocity and peak volumetric flow rate of stormwater runoff from the project site.

(B) Properties subject to Minimum Requirement No. 5 and/or No. 7 shall implement controls as early in the development as is practicable to mitigate for flow rates.

(C) Where necessary to comply with Minimum Requirement No. 7, stormwater retention/detention facilities shall be constructed as one of the first steps in grading. Detention facilities shall be functional prior to construction of site improvements (e.g., impervious surfaces).

(D) If permanent infiltration ponds are used for flow control during construction, these facilities should be protected from siltation during the construction phase.

(A) Design, install, and maintain effective erosion controls and sediment controls to minimize the discharge of pollutants.

(B) Construct sediment control BMPs (sediment ponds, traps, filters, etc.) as one of the first steps in grading. These BMPs shall be functional before other land-disturbing activities take place.

(C) Minimize sediment discharges from the site. The design, installation and maintenance of erosion and sediment controls must address factors such as the amount, frequency, intensity and duration of precipitation, the nature of resulting stormwater runoff, and soil characteristics, including the range of soil particle sizes expected to be present on the site.

(D) Direct stormwater runoff from disturbed areas through a sediment pond or other appropriate sediment removal BMP, before the runoff leaves a construction site or before discharge to an infiltration facility. Runoff from fully stabilized areas may be discharged without a sediment removal BMP, but must meet the flow control performance standard in subsection (F)(2)(e)(iii)(A) of this section.

(E) Locate BMPs intended to trap sediment on site in a manner to avoid interference with the movement of juvenile salmonids attempting to enter off-channel areas or drainages.

(F) Where feasible, design outlet structures that withdraw impounded stormwater from the surface to avoid discharging sediment that is still suspended lower in the water column.

(A) All exposed and unworked soils shall be stabilized by application of effective BMPs that protect the soil from the erosive forces of raindrop impact and flowing water, and wind erosion. Applicable BMPs include, but are not limited to: temporary and permanent seeding, sodding, mulching, plastic covering, erosion control fabrics and matting, soil application of polyacrylamide (PAM), the early application of gravel base early on areas to be paved, and dust control.

(B) Control stormwater volume and velocity within the site to minimize soil erosion.

(C) Control stormwater discharges, including both peak flow rates and total stormwater volume, to minimize erosion at outlets and to minimize downstream channel and stream bank erosion.

(D) From October 1st through April 30th of each year, no soils shall remain exposed and unworked for more than two days. From May 1st to September 30th of each year, no soils shall remain exposed and unworked for more than seven days. This condition applies to all soils on site, whether at final grade or not.

(E) Stabilize soils at the end of the shift before a holiday or weekend if needed based on the weather forecast.

(F) Minimize the amount of soil exposed during construction activity.

(G) Minimize the disturbance of steep slopes.

(H) Minimize soil compaction and, unless infeasible, preserve topsoil.

(I) Applicable practices include, but are not limited to, temporary and permanent seeding, sodding, mulching, plastic covering, soil application of polyacrylamide (PAM), early application of gravel base on areas to be paved, and dust control.

(J) Soil stabilization measures selected should be appropriate for the time of year, site conditions, estimated duration of use, and potential water quality impacts that stabilization agents may have on downstream waters or ground water.

(K) Soil stockpiles must be stabilized and protected with sediment trapping measures and, where possible, locate away from storm drain inlets, waterways and drainage channels.

(L) Work on linear construction sites and activities, including right-of-way and easement clearing, roadway development, pipelines, and trenching for utilities, shall not exceed the capability of the individual contractor for his portion of the project to install the bedding materials, roadbeds, structures, pipelines, and/or utilities, and to restabilize the disturbed soils, meeting the timing conditions listed above.

(M) In addition, at the discretion of the public works director, those sites unable to maintain the quality of their stormwater discharge may be required to provide soil stabilization to all exposed soil areas regardless of the working status of the area. Upon written notification, the property owner shall provide full stabilization of all exposed soil areas within 24 hours.

(A) Cut and fill slopes shall be designed and constructed in a manner that will minimize erosion. Applicable practices include, but are not limited to, reducing continuous length of slope with terracing and diversions, reducing slope steepness, and roughening slope surfaces (for example, track walking).

(B) Consider soil type and its potential for erosion.

(C) Reduce slope runoff velocities by reducing the continuous length of slope with terracing and diversions, reduce slope steepness, and roughen slope surface.

(D) Divert upslope drainage and run-on waters from off site with interceptors at top of slope. Off-site stormwater should be handled separately from stormwater generated on the site. Diversion of off-site stormwater around the site may be a viable option. Diverted flows shall be redirected to the natural drainage location at or before the property boundary.

(E) Contain down slope collected flows in pipes, slope drains, or protected channels to prevent erosion. Temporary pipe slope drains must handle the peak volumetric flow rate calculated using a 10-minute time step from a Type 1A, 10-year, 24-hour frequency storm for the developed condition. Alternatively, the 10-year one-hour flow rate predicted by an approved continuous runoff model, increased by a factor of 1.6, may be used. The hydrologic analysis must use the existing land cover condition for predicting flow rates from tributary areas outside the project limits. For tributary areas on the project site, the analysis must use the temporary or permanent project land cover condition, whichever will produce the highest flow rates. If using the Western Washington Hydrology Model to predict flows, bare soil areas should be modeled as “landscaped area.”

(F) Provide drainage to remove ground water intersecting the slope surface of exposed soil areas.

(G) Excavated material shall be placed on the uphill side of trenches, consistent with safety and space considerations.

(H) Check dams shall be placed at regular intervals within trenches that are cut down a slope.

(I) Stabilize soils on slopes, as specified in Element No. 5.

(A) All storm drain inlets made operable during construction shall be protected so that stormwater runoff shall not enter the conveyance system without first being filtered or treated to remove sediment.

(B) All approach roads shall be kept clean, and all sediment and street wash water shall not be allowed to enter storm drains without prior and adequate treatment unless treatment is provided before the storm drain discharges to waters of the state.

(A) All temporary on-site conveyance channels shall be designed, constructed and stabilized to prevent erosion from expected peak flows. Channels must handle the peak volumetric flow rate calculated using a 10-minute time step from a Type 1A, 10-year, 24-hour frequency storm for the developed condition. Alternatively, the 10-year peak flow rate, as determined by an approved continuous runoff model with a 15-minute time step, may be used. The hydrologic analysis must use the existing land cover condition for predicting flow rates from tributary areas outside the project limits. For tributary areas on the project site, the analysis shall use the temporary or permanent project land cover condition, whichever will produce the highest flow rates. If using the Western Washington Hydrology Model to predict flows, bare soil areas should be modeled as “landscaped area.”

(B) Stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent stream banks, slopes and downstream reaches shall be provided at the outlets of all conveyance systems.

(A) Design, install, implement and maintain effective pollution prevention measures to minimize the discharge of pollutants.

(B) All pollutants, including waste materials and demolition debris, that occur on site during construction shall be handled and disposed of in a manner that does not cause contamination of stormwater.

(C) Cover, containment, and protection from vandalism shall be provided for all chemicals, liquid products, petroleum products, and noninert wastes present on the site (see Chapter 173-304 WAC, as currently enacted or hereafter modified, for the definition of inert waste, which is incorporated herein by this reference).

(D) Maintenance and repair of heavy equipment and vehicles involving oil changes, hydraulic system drain down, solvent and de-greasing cleaning operations, fuel tank drain down and removal, and other activities which may result in discharge or spillage of pollutants to the ground or into stormwater runoff must be conducted using spill prevention measures, such as drip pans. Contaminated surfaces shall be cleaned immediately following any discharge or spill incident. Emergency repairs may be performed on site using temporary plastic placed beneath and, if raining, over the vehicle.

(E) Wheel wash, or tire bath wastewater, shall be discharged to a separate on-site treatment system or to the sanitary sewer.

(F) Application of agricultural chemicals, including fertilizers and pesticides, shall be conducted in a manner and at application rates that will not result in loss of chemical to stormwater runoff. Manufacturers’ recommendations shall be followed for application rates and procedures.

(G) Management of pH-modifying sources shall prevent contamination of runoff and stormwater collected on the site. These sources include, but are not limited to, bulk cement, cement kiln dust, fly ash, new concrete washing and curing waters, waste streams generated from concrete grinding and sawing, exposed aggregate processes, and concrete pumping and mixer washout waters.

(H) Adjust the pH of stormwater if necessary to prevent violations of water quality standards.

(I) Assure that washout of concrete trucks is performed off site or in designated concrete washout areas only. Do not wash out concrete trucks onto the ground, or into storm drains, open ditches, streets, or streams. Do not dump excess concrete on site, except in designated concrete washout areas. Concrete spillage or concrete discharge to surface waters of the state is prohibited. Do not wash out to formed areas awaiting infiltration BMPs.

(J) Obtain written approval from Ecology before using chemical treatment other than CO₂, dry ice, or food grade vinegar to adjust pH.

(K) Uncontaminated water from water-only based shaft drilling for construction of building, road, and bridge foundations may be infiltrated provided the wastewater is managed in a way that prohibits discharge to surface waters. Prior to infiltration, water from water-only based shaft drilling that comes into contact with curing concrete must be neutralized until pH is in the range of 6.5 to 8.5 (su).

(A) All foundation, vault, and trench dewatering water, which have similar characteristics to stormwater runoff at the site, shall be discharged into a controlled conveyance system, prior to discharge to a sediment trap or sediment pond. Channels must be stabilized, as specified in Element No. 8.

(B) Clean, nonturbid dewatering water, such as well-point ground water, can be discharged to systems tributary to state surface waters, as specified in Element No. 8, provided the dewatering flow does not cause erosion or flooding of the receiving waters. These clean waters should not be routed through sediment ponds with stormwater.

(C) Highly turbid or otherwise contaminated dewatering water, such as from construction equipment operation, clamshell digging, concrete tremie pour, or work inside a cofferdam, shall be handled separately from stormwater at the site.

(D) Other disposal options, depending on site constraints, may include, by way of example: (1) infiltration, (2) transport off site in vehicle, such as a vacuum flush truck, for legal disposal in a manner that does not pollute state waters, (3) on-site treatment using Ecology approved chemical treatment or other suitable treatment technologies, (4) sanitary or combined sewer discharge with local sewer district approval, or if there is no other option, (5) use of a sedimentation bag that discharges to a ditch or swale for small volumes of localized dewatering.

(A) All temporary and permanent erosion and sediment control BMPs shall be maintained and repaired as needed to assure continued performance of their intended function. All maintenance and repair shall be conducted in accordance with BMPs.

(B) Sediment control BMPs shall be inspected weekly or after a runoff-producing storm event during the dry season and daily during the wet season. All projects that disturb an area greater than one acre shall have a certified erosion control lead available to the site. This erosion control lead shall be responsible to provide overview of ongoing day-to-day erosion control requirements. The erosion control lead shall (within 24 hours) report to the city and Department of Ecology any site discharges that exceed state water quality standards that have or are likely to have entered waters of the state.

(C) All temporary erosion and sediment control BMPs shall be removed within 30 days after final site stabilization is achieved or after the temporary BMPs are no longer needed. Trapped sediment shall be removed or stabilized on site. Disturbed soil areas resulting from removal of BMPs or vegetation shall be permanently stabilized.

(A) Phasing of Construction. Development projects shall be phased where feasible in order to prevent, to the maximum extent practicable, the transport of sediment from the development site during construction. Revegetation of exposed areas and maintenance of that vegetation shall be an integral part of the clearing activities for any phase.

(B) When establishing these permitted clearing and grading areas, consideration should be given to minimizing removal of existing trees and minimizing disturbance/compaction of native soils except as needed for building purposes. Permitted clearing and grading areas and any other areas required to preserve critical or sensitive areas, buffers, native growth protection easements, or tree retention areas, shall be delineated on the site plans and the development site.

(C) Coordination with Utilities and Other Contractors. The primary project proponent shall evaluate, with input from utilities and other contractors, the stormwater management requirements for the entire project, including the utilities, when preparing the construction SWPPP.

(D) Inspection and Monitoring. All BMPs shall be inspected, maintained, and repaired as needed to assure continued performance of their intended function.

(E) For any project disturbing more than one acre, a certified professional in erosion and sediment control shall be identified in the construction SWPPP and shall be on site or on call at all times. Certification may be through the Washington State Department of Transportation/Associated General Contractors (WSDOT/AGC) Construction Site Erosion and Sediment Control Certification Program or any equivalent local or national certification and/or training program, in the city’s discretion.

(F) Whenever inspection and/or monitoring reveals that the BMPs identified in the construction SWPPP are inadequate, due to the actual discharge of or potential to discharge a significant amount of any pollutant, the SWPPP shall be modified, as appropriate, in a timely manner.

(G) Maintenance of the Construction SWPPP. The construction SWPPP shall be retained on site. The construction SWPPP shall be modified whenever there is a significant change in the design, construction, operation, or maintenance of any BMP.

(A) Protect all bioretention and rain garden BMPs from sedimentation through installation and maintenance of erosion and sediment control BMPs on portions of the site that drain into the bioretention and/or rain garden BMPs. Restore the BMPs to their fully functioning condition if they accumulate sediment during construction. Restoring the BMP must include removal of sediment and any sediment-laden bioretention/rain garden soils, and replacing the removed soils with soils meeting the design specification.

(B) Prevent compacting bioretention and rain garden BMPs by excluding construction equipment and foot traffic. Protect completed lawn and landscaped areas from compaction due to construction equipment.

(C) Control erosion and avoid introducing sediment from surrounding land uses onto permeable pavements. Do not allow muddy construction equipment on the base material or pavement. Do not allow sediment-laden runoff onto permeable pavements or base materials.

(D) Pavement fouled with sediments or no longer passing an initial infiltration test must be cleaned using procedures in accordance with the Ecology Manual or the manufacturer’s procedures.

(E) Keep all heavy equipment off existing soils under LID facilities that have been excavated to final grade to retain the infiltration rate of the soils.

3. Minimum Requirement No. 3 – Source Control of Pollution. All known, available and reasonable source control BMPs shall be applied to all projects. Source control BMPs shall be selected, designed, and maintained according to the Ecology Manual. Source controls that are applicable to a project shall be either indicated on the stormwater site plan and/or contained within a stormwater engineering report when such report is required.

4. Minimum Requirement No. 4 – Preservation of Natural Drainage Systems and Outfalls. Natural drainage patterns shall be maintained, and discharges from the project site shall occur at the natural location, to the maximum extent practicable. The manner by which runoff is discharged from the project site must not cause a significant adverse impact to downstream receiving waters and down gradient properties. All outfalls require energy dissipation. Additional information on how to comply with this requirement may be found in the Ecology Manual.

a. Applicability. Except as provided below, on-site stormwater management BMPs are required to be constructed in accordance with the following project thresholds, standards, and lists to infiltrate, disperse, and retain stormwater runoff on site to the extent feasible without causing flooding or erosion impacts.

Projects qualifying as flow control exempt in accordance with Minimum Requirement No. 7 shall either use the LID BMPs from List No. 3 for all surfaces within each type of surface in List No. 3; or use any flow control BMP(s) desired to achieve the LID Performance Standard, and apply BMP T5.13.

i. Projects triggering only Minimum Requirements No. 1 through No. 5 shall either:

(A) Use on-site stormwater management BMPs from List No. 1 of the Ecology Manual for all surfaces within each type of surface in List No. 1; or

(B) Demonstrate compliance with the LID performance standard. Projects selecting this option cannot use rain gardens. They may choose to use bioretention BMPs as described in the Ecology Manual and apply BMP T5.13.

ii. Thresholds. Projects triggering Minimum Requirements No. 1 through No. 9 shall meet the requirements stated in the Ecology Manual.

c. Low Impact Development Performance Standard. Stormwater discharges shall match developed discharge durations to predeveloped durations for the range of predeveloped discharge rates from eight percent of the two-year peak flow to 50 percent of the two-year peak flow. Refer to the standard flow control requirement section in Minimum Requirement No. 7 for information about the assignment of the predeveloped condition. Project sites that must also meet minimum requirement No. 7 shall match flow durations between eight percent of the two-year flow through the full 50-year flow.

a. Applicability. All projects subject to this minimum requirement shall utilize on-site stormwater BMPs for the treatment of runoff. Additionally, when the following design thresholds are met or exceeded within a threshold discharge area, an engineered water quality facility shall be provided. All runoff treatment facilities and BMPs shall be designed, sized and provided for in accordance with the Ecology Manual.

b. Thresholds. When assessing the applicability of Minimum Requirement No. 6, only consider those hard and pervious surfaces listed below.

i. The following require construction of stormwater treatment facilities:

(A) Projects in which the total of new, replaced or new plus replaced effective pollution-generating hard surface (PGHS) is 5,000 square feet or more in a threshold discharge area of the project; or

(B) Projects in which the total of new, replaced or new plus replaced effective pollution-generating pervious surfaces (PGPS) – not including permeable pavements – is three-quarters of an acre or more in a threshold discharge area, and from which there will be a surface discharge in a natural or manmade conveyance system from the site.

ii. Additional thresholds for oil control, phosphorus treatment, enhanced treatment, and basic treatment are stated in the Ecology Manual.

c. Additional Requirements. Direct discharge of untreated stormwater from pollution-generating hard surfaces to ground water is prohibited, except for the discharge achieved by infiltration or dispersion of runoff from residential sites through use of on-site stormwater management BMPs in accordance with Chapter 5, Volume V and Chapter 7, Volume V of the Ecology Manual; or by infiltration through soils meeting the soil suitability criteria in Chapter 3 of Volume III of the Ecology Manual. Projects within Basin One of the Lake Whatcom watershed shall meet these standards for water quality in addition to those contained in other portions of this code.

a. Applicability. Projects must provide flow control to reduce the impacts of stormwater runoff from hard surfaces and land cover conversions. All projects subject to this minimum requirement shall utilize on-site stormwater BMPs for flow control. Additionally, when the following design thresholds are met or exceeded, an engineered water quantity facility shall be provided. All water quantity facilities and flow control BMPs shall be designed and provided for in accordance with the Ecology Manual. The thresholds and requirements below apply to projects that discharge stormwater directly or indirectly into fresh water. Those projects that meet flow control exemption criteria of the Ecology Manual are eligible to apply for modification to these requirements. Exception: The exemption of flow standards for Lake Whatcom shall only be allowed with the written approval of the public works department. The basis of that approval shall be a finding that no appreciable risk of water quality degradation will result from the exemption.

b. Thresholds. When assessing the applicability of Minimum Requirement No. 7, consider the following:

i. Projects in which the total of new, replaced or new plus replaced effective hard surfaces are 10,000 square feet or more in a threshold discharge area; or

ii. Projects that convert three-fourths acres or more of native vegetation to lawn or landscape, or convert two and one-half acres or more of native vegetation to pasture in a threshold discharge area, and from which there is a surface discharge in a natural or manmade conveyance system from the site; or

iii. Projects that, through a combination of new, replaced or new plus replaced effective impervious surfaces and converted pervious surfaces, cause a 0.15 cubic feet per second (cfs) or greater increase in the 100-year flow frequency as estimated using an approved continuous simulation model and 15-minute time steps; or

iv. Projects within Basin One of the Lake Whatcom watershed.

c. Standard Flow Control Methodology. Stormwater discharges shall match developed discharge durations to predeveloped durations for the range of predeveloped discharge rates from 50 percent of the two-year peak flow up to the full 50-year peak flow. The predeveloped condition to be matched shall be a forested land cover unless reasonable, historic information is provided that indicates the site was prairie prior to settlement (modeled as “pasture” in the Western Washington Hydrology Model); or

This standard requirement is waived for sites that will reliably infiltrate all the runoff from hard surfaces and converted vegetation areas.

d. Flow control BMPs shall be selected, designed, and maintained according to Volume III of the Ecology Manual.

8. Minimum Requirement No. 8 – Wetlands Protection. Projects shall employ stormwater management BMPS in accordance with the thresholds, standards, and requirements in Ecology Manual to reduce the impacts of stormwater runoff to wetlands.

9. Minimum Requirement No. 9 – Operation and Maintenance. An operation and maintenance manual that is consistent with the provisions within the Ecology Manual shall be provided for all proposed stormwater facilities and BMPs, and the party (or parties) responsible for maintenance and operation shall be identified. At private facilities, a copy of the manual shall be retained on site or within reasonable access to the site, and shall be transferred with the property to the new owner. For public facilities, a copy of the manual shall be retained in the appropriate department. A log of maintenance activity that indicates what actions were taken shall be kept and be available for inspection by the city or Ecology.

G. Financial Liability/Public Nuisance Declared. In addition to other remedies, failure to install and/or maintain stormwater facilities as required in this chapter and applicable permits is hereby declared to be a public nuisance, subject to abatement as provided by applicable laws of the city or the state of Washington. The property owner and all persons engaged in development or land-disturbing activity shall be liable, jointly and severally, for all costs incurred by the city in any public nuisance action taken hereunder, or on account of damage or threatened damage to city property or facilities or water bodies, or associated with remedial actions necessitated by the failure to install and/or maintain required stormwater facilities. [Ord. 2022-05-013 § 1; Ord. 2017-03-009 § 4; Ord. 2009-06-041; Ord. 2006-05-047].